Geomorphosite of nui chua national park ninh thuận, viet nam

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GEOMORPHOSITES OF NUI CHUA NATIONAL PARK,
NINH THUAN PROVINCE, VIETNAM

Hoang Thi Phuong Chi 1,2*, Ha Quang Hai1,2, Nguyen Thi Que Nam1,2
1Faculty of Environment, University of Science, Ho Chi Minh City, Vietnam
2Vietnam National University, Ho Chi Minh City, Vietnam

* Corresponding author: Hoang Thi Phuong Chi
Faculty of Environment, University of Science, Vietnam National University – Hochiminh
city, Email: , Address: 227 Nguyen Van Cu street, Ward 4, District 5,
Hochiminh city, Vietnam

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Abstract

Nui Chua National Park, Ninh Thuan province, has a semi-arid climate while locating right
next to a tropical forest climate, therefore, it has a rich biodiversity ecosystem, where the
coastal dry forest ecosystem is rarely seen in Vietnam. This area contains many valuable
geomorphologic features in denuded - lithological - tectonic terrain, among them, three features
can be considered as national treasures: 1) Nui Chua dome - block mountains; 2) Rai Cave
tectonic - abrasive coastline and 3) Lang Choi Stone Park. Fault-block Nui Chua Mountains is
the unique geomorphosite of Vietnam which has the right conditions for the dry ecosystem to
develop. The tectonic - abrasive coastline of Rai Cave and Lang Choi Rock Park is home to
unique and precious geoheritages such as two-stage development of boulders or balanced
rocks, karren sculpturing, caves, notches on ancient coral reefs terrace or spheroidal
weathering, tafoni on intrusive rocks, to name a few. To archive the goal of sustainable
development, it is important to link the conservation activities of the biodiversity at Nui Chua
National Park to the preservation efforts of geological diversity (geology, geomorphology) in
the area. Providing scientific explanations at each geomorphosites together with safe
sightseeing guides will help increase the quality of tourism, attract more visitors to explore and
learn about this mysterious, wonderful, and diverse ecosystem.
Keywords: geomorphosites, denuded - lithological - tectonic terrain, Nui Chua National Park,
Ninh Thuan province
Introduction
The term "geomorphosites", often used to refer to geomorphological heritage, is the
abbreviation of "geomorphological sites" (Panizza, 2001; Pralong, 2005). Compared with
geological heritages, geomorphologic heritage has three specific main characteristics:
aesthetics, dynamics, and overlap in scale (Reynard, 2009). The above three characteristics
mean these geoheritages are beautiful, active landforms, and vary in area from small to large.
These features make the geomorphologic heritage unique and attract visitors to admire and
explore. Over the past three decades, scientific studies have been carried out in many parts of
the world, focusing on the scientific and complementary values of the geological and
geomorphological heritages (Brilha, 2016; Fuertes-Gutiérrez and Fernández-Martínez, 2012;
Mihai Ielenicz, 2009; Nickolas C. Zouros, 2007). Like other geological heritages,
geomorphologic heritages deserve to be protected and preserved to pass on to future

generations.
Nui Chua National Park area has the driest climate in Vietnam, and has rich biodiversity both
in mountainous and coastal areas. Major tourist attractions within the Nui Chua National Park
such as Vinh Hy Bay, Rai Cave, Chua Mountains, and so on, can be considered as
geomorphosites (Figure 1).
Although Nui Chua National Park has been open for visitors for a long time, these tourist
attractions have not been extensively studied in terms of scientific and complementary values.

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As a consequence, these geomorphosites still face problems with attracting a variety of visitors
as well as long-term solutions for protection and conservation.
Within this work, the scientific and additional values of geomorphosites in Nui Chua National
Park are investigated and presented. This valuable information of these heritages would help
to attract not only more visitors but also students and scientists to perform more thorough
investigation about this National Park
Methods

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The research is conducted based on the inventory of geomorphosites, followed the guideline of
Reynard et al., 2016, 2007 as steps below:

(1)Literature review about geology and geomorphology in journals, books, and the Vietnam
geological - mineral map, Da Lat - Cam Ranh, 1:200,000 scale (Vietnam Department of
Geology and Minerals, 1998).
(2)Potential sites were chosen to fieldwork for the detailed descriptions of each site included:
location, information on geology and geomorphology, accessibility, present uses and
infrastructure, protection, condition of the outcrop (visibility), other information (ecological,
cultural, historical, economic values) and photographic documentation.
(3)The preliminary assessment was conducted to pick out sites that have scientific and
additional values following the criteria proposed by Reynard. The scientific values consist of
four criteria: representativeness, unique/rareness, integrity and paleogeographical value
(detailed explanation and references of these criteria are shown in Table 1); the additional
values include three main criteria: ecology, aesthetics (viewpoints, contrasts, vertical
development, and space structuration), and culture (religious, historical, artistic, literary,
geohistorical, and economic importance). In this step, we chose 12 sites that have values to be
geomorphosites in this study area.
(4) The heritages are classified according to three levels: local (Ninh Thuan province), regional
(South Central coast of Vietnam), and national (Vietnam): based on the representativeness
or/and rareness of site in each scale. Besides that, we consider other scientific and additional
values to suggest the level of geomorphosites.

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Table 1. The scientific value of geomorphosite
Criterion
Scientific value
Representativeness A selected geomorphosite
should represent the most
complete and expressive

manifestation of a
geomorphological
phenomenon or a spatialgenetic pattern.

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Rareness/ Unique

Concerns the rarity of the site
with respect to a reference
space.
This criterion of a site can
depend on different
indicators: on quantitative
parameters, or on qualitative
parameters; on spatialtemporal indicators.

Example in research area
Da Chong inselberg is 86 m high
mountain. It has many large rounded
granite boulders which precariously
balanced on top of another. This site
is representative for the balanced
rocks in the study area and the
South-Central Coast of Vietnam also.
Thit Beach is quite different from
other beaches in this region because
of its good conditions for sea turtles

spawning. The rareness of the sandy
beach is the highest value of this site.

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State of conservation of the
site.

Most of the sites in this area belong
to national park, therefore, they are
protected. by management boards.
Palaeogeographical Importance of the site for the Hon Do Cape has an ancient coral
value
Earth or climate history
reef terrace. The 4 – 5 m high marine
terrace represented the Quaternary
tectonics and East sea level changing
activities.
(According to Brilha, 2016; Nickolas C. Zouros, 2007; Pereira and Pereira, 2010; Pralong,
2005; Reynard et al., 2016, 2007; Wimbledon W.A.P. et al., 2000).

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Integrity

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Research area
Nui Chua National Park locates in the Northeastern part of Ninh Thuan province. The national
park borders the Cam Ranh Bay - Khanh Hoa on the north, the East Sea on the east, Ninh Hai
district on the south, and the highway 1A on the southeast. Nui Chua National Park includes
Ninh Hai district, about a quarter of Thuan Bac district in Ninh Thuan province with an area
of 29.856 ha, of which 22.513 ha is land, 7.352 ha is the sea. Two roads with easy access to the
geomorphological features are the national highway 1A and the provincial road 702. Besides,
the North-South railway, which runs parallel to the national highway 1A and the sea, is another
convenient transportation method to visit the national park.

Figure 1. Geological map of Nui Chua National Park (modified from Vietnam Department
of Geology and Minerals, 1998)

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Geology and geomorphology
The Cretaceous Deo Ca intrusive complex occupies most of the studied area and has the Da
Lat Late Mesozoic active continental margin structure (Tran Van Tri and Vu Khuc, 2009). The
main intrusive rock are granite, granosyenite, and granodiorite (Nguyen Duc Thang, 1999).
Nui Chua Mountain is composed of intrusive rocks with six peaks. Among those, the highest
is Co Tuy (1,039m), also known as Chua Anh Mountain (means older brother). The 5 other
peaks are named Chua Chong Mountain (means husband), Chua Vo Mountain (means wife),
Chua Em Mountain (means younger brother), Chua Chau Mountain (means grandchild), and
Chua Chat Mountain (means great-grandchild). Holocene marine sediments occupy only a
small area in the south and include sand, gravel, coral debris, and coral reefs. These
sedimentsform a 4 – 5 m high marine terrace, which is equivalent to the Ca Na terrace that was
formed in the Flandrian transgression stage (Le Duc An, 2012). Orthogonal joint systems
included two vertical systems dominantly in the direction 1) NE-SW, NW-SE and 2) sublongitude, sub-latitude and horizontal system. The processes of denudation were developed
according to the joint systems that cut into the intrusive rock bed, which were the basis for
forming the typical boulder of the area.

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Climate and hydrography
According to “Köppen-Geiger Climate Classification” the study area belongs to the tropical
savanna climate entirely (Kottek et al., 2006). Ninh Thuan province has two distinct seasons:
the rainy season from September to December and the dry season from January to August. The
average temperature ranges from 24.6 to 27.2 C. There is a distinct dry season, where there
will be no rain for months. Then a short rainy season brings heavy rains mostly in the
afternoons, with hot, humid conditions throughout the rest of the day. Even with the rainy
season, the annual rainfall is the lowest rainfall in South-Central Vietnam (430-940 mm), while
the evaporation is quite high (1295.8-2210.1 mm), twice as much as the rainfall (Tu Thi Nam
et al., 2018). The streams and springs in the national park are narrow, seasonal flow from the
Nui Chua Mountain into the sea. Most of the streams dry up during the dry season. The tidal
patterns that occur along the Ninh Hai district coastline are irregular diurnal tides. The average
amplitude of tides is about 0.8-1.2 m, with the highest is over 1.5 m (Pham Ngoc Quy et al.,
2011). From January to April, the prevailing winds blow southwest, the average wave height
is 1.0-1.1 m with the maximum is about 2.0 m. From October to December, winds prevail from
the Northeast, the average wave height is about 1.2 m and the maximum is about 2.5 m. The
studied area is located in Ninh Thuan - Bac Binh Thuan upwelling zone, which occurs from
June to September. Upwelling brings nutrients into the surface water of the ocean, results in
some of the most productive marine ecosystems (Nguyen Kim Vinh, 2007).
Ecology:
Nui Chua National Park is located in the driest part of Vietnam therefore it has the typical and
unique dry forest ecosystems rarely seen in Vietnam and Southeast Asia. According to Duc et
al., 2009, the only primary forest that remains is evergreen forest at elevations > 700 m above
sea level in the north of the park. Below 700 m above sea level, on the east side of the mountains
there are large areas of four types of secondary forest such as sclerophyll evergreen forests, dry
deciduous forest and tropical savanna woodland, dry thorny scrub and thorny woodland; thorny
scrubland (Duc et al., 2009).
Nui Chua National Park has 1,504 vascular plant species. In terms of fauna, it currently has
306 species of animal, of which 64 are rare and conserved species (Tran Van Tiep and Dang
Thi Thanh Thuy, 2014). There are several species such as Red-shanked Douc Langur

(Pygathrix nemaeus) was listed in the Red List of IUCN as Endangered Asian colobine monkey
(Craig Hilton-Taylor (Compiler), 2000). The coastal reefs are in relatively good condition,
including 310 species (Si Tuan Vo et al., 2014). In addition, Nui Chua National Park is one of

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the rare inland spawning beaches for sea turtles ((Tran Van Tiep and Dang Thi Thanh Thuy,
2014).
Results and discussion
Geomorphosites
Conducting inventories and field surveys, we identified 12 geomorphosites which can be
classified into five types: (1) mountains, (2) bays and lagoons, (3) marine terraces, (4) rocky

coastline, and (5) beaches. The scientific and additional values are shown in Figure 2 and
summarized in Table 2.
The common geomorphosites are balanced rocks (which are composed of two or more
boulders, perched one on the other (Twidale and Vidal Romaní, 2005)) in denuded products of
which dominant factors are orthogonal joints system and homogeneous material of intrusive
rock bodies. These can be called denuded - lithological – tectonic terrain in mountainous areas
and abrasive – lithological – tectonic terrain in lower coastal areas. In addition, the system of
fractures is oriented to extend the coastline, currents, bays, and lagoons.

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Figure 2. Geomorphosites of Nui Chua National Park - Ninh Thuan provinceTable 2. Summary of scientific value and additional value of
geomorphosites in Nui Chua National Park - Ninh Thuan

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Geomorphosites
name

Nui Chua dome block mountain

Ca Du inselberg

Sym
bol

G.3

G.8

Scientific Values
+ Geomorphology:
- Five blocks of different altitudes: central block 8001039 m high, two adjacent blocks: 800-400 m, two
outmost blocks: 400-100 m.
- Erosive-denudate terrain on intrusive rocks: the twostage development of boulders, rock water stream,
hanging lake, waterfall, bay etc.
- Quaternary tectonic
+ The most important criteria:
Integrity, Rareness and Representativeness: All the
landforms are in good conservation in national park
+ Geomorphology:
- Inselberg on Phan Rang plain, 318 m high.
- Large rounded granite boulders precariously
balanced on top of another.
+ The most important criterion:Integrity: good
conservation

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Da Chong
inselberg

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Additional Value

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+ Ecological value: three distinct ecosystems with National
rich biodiversity, including: marine, dry forest and
evergreen forest.
+ Aesthetic value: spectacular landscape spanning
from hill to mountain to ocean.

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+ Geomorphology:
- Inselberg on Phan Rang plain, 86 m high.
- Large rounded granite boulders which precariously
balanced on top of another
G.10 + The most important criterion:
This site is representative for the balanced rocks in
the South-Central Coast of Vietnam

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Heritage
Level

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+ Aesthetic value:
Local
- Ca Du - a turtle shaped mountain (in Cham
language is Chơk Du ').
- Panoramic viewpoint: Phan Rang - Thap
Cham town, Ninh Chu coast, Phuong Cuu
salt field, Dam Vua lagoon, Ninh Hai rice
field and Da Chong mountain.
+ Cultural value: the Revolutionary war historical
memorial of Ninh Thuan province (1999).
+ Aesthetic value: viewpoint of Ninh Chu beach,
Regional
Ninh Hai rice field.
+ Cultural value:
- the historical monument of Ninh Thuan
province.
- the system of pagodas has unique architecture
such as Trung Son pagoda, Trung Quang pagoda,
Temple of Confucius, Truc Lam Vien Ngo
monastery

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Vinh Hy erosion
tectonic bay

Nai lagoon

G.4

G.9

Lang Choi
abrasion marine
terrace, abrasive
effect of
sediments

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+ Geomorphology:
- Vinh Hy Bay was formed by the wave-destruction
on the northwest-southeast joinsystem. This happened
before the Flandrian transgression.
- The bay deeply penetrates in the mainland, and is a
connection point for the mountainous and marine
ecosystem.
+ The most important criterion:
This site is representative for the erosion tectonic bay
in the South-Central Coast of Vietnam

+ Geomorphology:
- Nai bay is shallow bodies of water separated from
the ocean by sandbars.
- Function of regulating flood flow, balancing
groundwater and cleaning the environment.
+ The most important criterion:
This site is representative for the lagoon in Ninh
Thuan province.
+ Geomorphology:
- Cliffs are oriented in sub-longitude fault .
- The two-stage development of boulders or balanced
rocks are common. The height is 80-100 m.
- The largest granite boulders precariously balanced
on top of another is the symbol of Nui Chua National
Park.
- Tafoni on granite.
+ The most important criteria:
Unique, Rareness, Representativeness: This site is the
only occurrence of 80 -100 m high marine terrace in
the the South-Central Coast of Vietnam.

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+ Aesthetic value: proincial level landscapes.
+ Ecological value: coral is diverse and well
preserved.
+ Cultural value: tourism; lobster farming

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Regional

+ Aesthetic value: impressive sunset landscape.
+ Ecological value: rich diversity, 300 ha of
mangrove forest.
+ Cultural value: aquaculture, potential for
tourism development.

Local

+ Aesthetic value: the dry forest landscape
together with balanced boulders.
+ Ecological value: typical xeric plants: thick
leaves, rough, and spiky stems.

National

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Ninh Hai marine
terrace, sediment
accumulation

Da Vach tectonic
cliff

Rai Cave
abrasion tectonic
cliff

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Hon Do cape,
ancient coral reef

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+ Geomorphology:
+ Cultural value:
- Marine accumulation terrace in Flandrian
- sea salt farms, rice fields, specialty crops:
transgression, 4-5 m high.
grapes, garlics, chilies, spring onions.
- Urban infrastructure foundations, residential areas,
- the Nam Hai Mausoleum Festival which prays
G.11
salt fields.
for good weather and good harvest.
+ The most important criterion:
This site is representative for the marine terrace in
Ninh Thuan province.
+ Geomorphology:
+ Aesthetic value: The landscape of majestic
cliffs.
- A steep cliffs 20-50 m in height and 5 km in length
is oriented in longitude fault.
G.2 - Wave-cut cliffs resulted in carved terrain with many
unique shapes.
+ The most important criterion:
This site is representative for the tectonic cliff in the

South - Central Coast of Vietnam.
+ Geomorphology:
+ Aesthetic value: the provincial natural landscape
monuments of Ninh Thuan province (2018).
- Cliffs are oriented in sub-longitude fault.
- Diverse coastal terrains: cliffs, marine terraces,
+ Ecological value: rich biodiversity, especially
balanced boulders, cave, wave-cut notch, razor-sharp the coral reefs.
and jagged coral rock, Karren terrain.
+ Cultural value: potential for sustainable tourism
G.5
development.
- Ancient coral reef terrace, 4-5 m in height
+ The most important criteria:
Unique and palaeogeographical value: This site is the
only occurrence of tectonic cliff coast and coral reef
terrace in Vietnam.
+ Geomorphology:
+ Aesthetic value: beautiful coastal landscapes
- Red sand overlay on coral rock.
+ Ecological value: rich biodiversity, especially
the coral reefs.
- Wave-cut notch, razor-sharp and jagged coral rock,
G.12
karren terrain.
+ Cultural value:
+ The most important criterion:
- the Temple of Lady Do belongs to Cham
Palaeogeographical value of ancient coral reef terrace culture

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Local

Regional

National

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Regional

-

Nuoc Ngot beach

G.1

G.6

Thit beach

+ Geomorphology:
- Pocket beach with coarse sediment.
- Fresh water springs from Nui Chua mountains.
+ The most important criterion:
Rareness of the landscape: the unique spring meets
the sea.
+ Geomorphology: Pocket sandy beach.
+ The most important criterion:
Rareness of the sandy beach: The beach has good
conditions for sea turtles spawning.

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+ Aesthetic value: the beauty of pristine beach.

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+ Ecological value:
- sea turtle conservation
- ecosystem of coastal coral reefs has a diversity
of species.

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Archeology in Cham cultural relics.

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Regional

Regional


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National level geomorphosites proposal
The most criterion for the selection of these national-level heritages is their rarity or/and
representativeness. Besides that, we consider other scientific and additional values to suggest
the level of geomorphosites. Proposing three national-level geomorphosites including 1) Dome
- block Nui Chua mountains, 2) Tectonic - abrasive coastline Rai Cave and 3) Lang Choi

abrasive marine terrace.
Dome-block Nui Chua Mountains
According to Nguyen-Van et al. (2020), the study area has four main fault scarps inland. These
fault scarps are shown in Fig. 3. The NE-SW faults FI, FII, FIII, and FIV (Figure 3, Figure 4)
are the boundaries of the main central block. The Nui Chua dome - block mountains were
uplifted in the Quaternary tectonic period to form the central block 800-1039 m high (the top
of Nui Chua Mount.), and lower to both sides are the 400-800 m and 100-400 m high. The
longitudinal faults are clearly shown, which are the boundaries of small blocks and orient many
sections of the coast, in which faults F2, F3, and F4 were confirmed by field survey (NguyenVan et al., 2020; Trinh et al., 2015). The NW-SE faults are oriented to stretch the bays such as
Cam Ranh bay, Vinh Hy bay, and Dam Nai lagoon.

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Figure 3. Interpretation of fault scraps on 12.5 m ASTER DEM image (according to NguyenVan et al., 2020; Trinh et al., 2015)
(“Dataset: ©JAXA/METI ALOS PALSAR, ALPSRP139313380. Accessed through ASF
DAAC,” n.d.).

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Dome - block mountain is one of the common landforms on the Vietnamese mainland (Le Duc

An, 2012). Another outstanding scientific value of this geomorphosite is the processes of
denudation on the intrusive rock along with fault systems. These fissures created specific
terrains such as two-stage development of boulders, cliffs, rock-hanging lakes (Figure 5), rock
water streams (Figure 6), bay, and waterfall. The Nui Chua Mountains ecosystem is diverse
with six ecosystems ranging from land to sea. It has a dry forest ecosystem, which is typical of
Vietnam and Southeast Asia (Le Tran Chan and Nguyen Viet Luong, 2012). The spectacular
trekking route through Nui Chua that passes through the geomorphologic landscapes from
mountains, to coastlines with these ecosystems has been carried out by many groups of
adventurous tourists (Figure 7). One of the most popular trekking routes is the one from the
National Park headquarters to the top of Nui Chua mountain in 3 days and 2 nights with a total
length of about 19.5 km. The trekking route is designed to go through the geomorphosites from
the coast of Rai Cave, Lo O stream, O Lim valley, through the topographic steps of Mount
Chua such as grassland, rock-hanging lake, to the top of Mount Chua Anh (Co Tuy) where a
panoramic view from the highest peak of the park can be observed. The landscape and ecology
are additional values of Nui Chua National Park.

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Figure 4. A part of Nui Chua Mt. is graded by Figure 5. Hanging lake. Source: Nui
the fault boundary. Source: Nui Chua National Chua National Park
Park

Figure 6. Lo O rock water spring. Source: Figure 7. Trekking in Nui Chua National
H.T.P.Chi
Park. Source: Nui Chua National Park

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Tectonic - abrasive coastline Rai Cave
Rai Cave is a famous tourist destination of Nui Chua National Park. Two geomorphosites that
attract tourists the most are the intrusive rocky coast and ancient coral reef. The rocky coast is
a fault stretching in the longitudinal direction (Figure 8), including many types of landforms
such as sea cliffs, balanced rocks, falling rocks, caves. The seawall profile shows the balanced
rocks pattern, a typical landform developed in intrusive rock corresponding to the second phase
(Figure 8A) and third phase (Figure 8B) according to Geikie's classification (Twidale and Vidal
Romaní, 2005). The activities of denudation in the Rai Cave coastline are strongly underway
with the formation of steep cliffs and large residual boulders. The space between falling rocks
often forms caves. These caves were once inhabited by otters, and therefore, this place had the
name “Rai Cave” – which means Otters’ cave.

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Figure 8. Longitudinal rocky coast, A – Orthogonal fissures (vertical and horizonal) on a
vertical wall); B – Expansion crack, falling rock blocks leaving balanced rocks; C – Rock falls
accumulating at the bottom; D – Ancient coral terrace. Source: Ha Quang Hai

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The ancient coral terrace is located at the cliff base (Figure 9), has an area of about 2000 m2,
the platform is quite flat, 4-5 m high above sea level. Noteworthy, the ancient coral reef
contains various limestone micro-landforms which attract tourists such as razor-sharp; jagged
coral rock (Figure 10); bio-abrasive pits (Figure 11); pot holes and heart pits which were
formed due to salt weathering. There is no data on the age of the terrace, but by comparing the
elevation, this terrace is equivalent to Ca Na 2nd terrace, where the corals have an absolute age
of 4500 ± 250 years (Le Duc An, 2012) and were formed in the maximum Flandrian marine
transgression. Aesthetics are the outstanding additional value of Rai Cave geomorphosite. The
great seascape at dawn and dusk. Especially during the rough seas, visitors can admire the
waterfalls when the seawater overflows the ancient coral terrace (Figure 12). Scientific and
aesthetic value shows that Rai Cave is the only rare and unique geomorphologic heritage of
Vietnam. Rai Cave was chosen to be the Nui Chua National Park Management Board
headquarter, where visitors can learn about the National Park and its forest and marine
conservation efforts.

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Figure 9. Ancient coral rock terrace. Source: Figure 10. Razor-sharp, jagged coral rock.
Ha Quang Hai
Source: H.T.P.Chi

Figure 11. Wave-cut notch in ancient coral Figure 12. Waterfall into sea. Source: Thien
terrace. Source: Ha Quang Hai
Thach(“Rai Cave - Ninh Thuan once and
forever | TTC Resort - Ninh Thuan,” n.d.)

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Lang Choi abrasive marine terrace
The abrasive marine terrace is known as Lang Choi Stone Park and is located in Vinh Hai
commune, Ninh Hai district. Lang Choi Stone Park has a total area of about 90 hectares, 80100 meters above sea level. The cliffs in the stone park are steep 70-80 degrees, and oriented
in a longitudinal direction as fault F4 in Figures 3 and 13. The fissure system is dominated by
fault F4 direction, which can be seen clearly in the topography (Figure 14). On the roof of the
terrace, there are various sizes and shapes of granite boulders. The most popular tourist
attraction is ‘Da Trung’ (means egg stone, Figure 15), ‘Dau Nguoi’ (means head), ‘Con Vit’
(means duck), and ‘Cu Hanh’ (means onion), which were named based on the shapes of
boulders. The biggest balanced rock is called 'Than Quyen’ (means theocracy, Figure 16), and
it is chosen as the symbol of Nui Chua National Park. The ‘Than Quyen’ rock is the slightly

less well-rounded boulder, nearly 6,0 m in diameter. This rock was finely balanced, and
therefore, the 'Than Quyen' rock is a visual model that explains the formation of denuded lithological - tectonic terrain and balanced rock, the typical landform of this area. If in Rai
Cave, we can observe the formation of boulders in the 2nd and 3rd stage (Figure 8 and 17 ii,
iii), in Lang Choi Stone Park, this process belongs to the 3rd stage (Figure 17 iv) due to
differential erosion of the differentiated mass, leaving the core stones as boulders (Figure 18)
(Geikie's (1894) sketch in Twidale and Vidal Romaní, 2005). The physical and chemical
weathering process resulted in the very impressive formation of the tafoni on granite.

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Figure 13. Longitudinal direction cliffs as F4 fault. Figure 14. Longitudinal joint. Source: Ha Quang
Source: Le Tu Thanh
Hai

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Figure 15. Balanced well-rounded boulder in Lang Figure 16. Orthogonal fissures on ‘Than Quyen’
Choi Stone Park. Source: Ha Quang Hai
boulder (vertical and horizontal). - Symbol of Nui
Chua National Park. Source: Ha Quang Hai

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Figure 17. Explain the formation stages of balanced rock according to Geikie (1894)
(i) Water penetrates down joint in
(ii) weathered granite
(iii) erosion removed debris and clay,
solid granite.
leaving behind corestones.

(iv) leaving the corestones as boulders

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Figure 18. Several equilibrium rocks in Lang Choi stone park. Source: Hoang Thi Phuong Chi

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Dry forests are the outstanding additional value of this geomorphosite. Low, small, thick,
thorny plants grow through fissures - a vivid example of biological weathering by physical

means (Figure 12). The rocky terrain and dry forests on the abrasive marine terrace of Lang
Choi Stone Park can be seen as a miniature part of Nui Chua National Park Reserve.

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Figure 19. Tafoni on intrusive rock. Figure 20. Cactus grew up in a fissure.
Source: Ha Quang Hai
Source: Ha Quang Hai
The need for a plan to preserve the geomorphologic heritage and safe tourism

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While biodiversity is strictly conserved in Nui Chua National Park, geomorphosites are widely
open to tourist activities. Additionally, the foundation of biodiversity of the national park has
not been fully studied and preserved. Some geomorphosites are being degraded due to natural
and human impacts, for example, the Cave Rai tectonics - abrasion geomorphosite.
Specifically, the ancient coral terrace in this area is being destroyed in large pieces by waves
(Figure 9) where a corroding hollow deepened into the platform wall. Moreover, allowing
visitors to walk on the platform has destroyed most types of micro-terrain such as razor-sharp,
jagged coral rock, mug, and pot holes (Figure 21).
The precarious rocks on the steep seawall, or the stacked rocks always pose potential risks to
visitors while visiting these sites. Therefore, wider concrete roads through Lang Choi Rock
Park and a path along the sea wall were constructed to provide a safer way for tourists. Yet,
these roads causes damage of the heritages’ integrity and do not entirely ensure safety for

visitors. (Figure 22).

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Figure 21. Micro-topography on the Figure 22. The wooden path along the cliff
ancient coral terrace was destroyed by wall for visitors in Rai Cave geomorphosite.
tourists. Source: Ha Quang Hai
Source: Ha Quang Hai
Nui Chua National Park is attracting more and more visitors, scientists to do research, and
students from universities to learn about its biodiversity. In the future, when recognized as a
UNESCO Biosphere Reserve, the number of people coming to Nui Chua National Park will
increase significantly, so a program of geoconservation, visitor safety at the same time
conservation of the ecosystems of Nui Chua National Park should be properly planned and
implemented soon so that both living and non-living resources can be protected together.
Conclusion

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Nui Chua National Park, where the climate is harsh, the land is arid and the hard rock is inert,
has extremely rich and diverse biological resources, in which the dry forest ecosystem is
considered the standard model, the most unique of Vietnam as well as Southeast Asia. Nui
Chua National Park also has geomorphosites which are characterized by denuded – lithological
– tectonic terrain, of which three nationally worthy heritages are: 1) Fault-block Nui Chua
Mountains; 2) Rai Cave tectonic – abrasive coastline and 3) Lang Choi Stone Park. Nui Chua
dome – block mountain is the only geomorphosite of Vietnam that converges the right
conditions for the unique dry ecosystem to arise and develop. The tectonic – abrasive coastline
of Rai Cave and Lang Choi Stone Park with the clearly shown balanced rocks; razor-sharp,
jagged coral rocks; caves; grazing hollows on ancient coral reefs; and physical, chemical
weathering tafoni on intrusive rocks; are the heritages of rare and precious types.
With the goal of sustainable development, the biodiversity conservation activities of Nui Chua
National Park need to be linked with the conservation of geological diversity (geology,
geomorphology). Providing scientifically interpreted geomorphological heritages at attraction
sites together with safe sightseeing guides will help improve the quality of the tour at each
destination, attracting more visitors to visit and learn about this mysterious and amazing
ecosystem.

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Acknowledgements
Hoang Thi Phuong Chi was funded by Vingroup Joint Stock Company and supported by the
Domestic Master/ PhD Scholarship Programme of Vingroup Innovation Foundation (VINIF),
Vingroup Big Data Institute (VINBIGDATA), code 2020.TS.117”
We also thank reviewers and editors for carefully corrections and suggestions. The English
editing of the manuscript was made by Dr. Tran Dieu Ly who is also acknowledged.

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GEOMORPHOSITES OF NUI CHUA NATIONAL PARK,
NINH THUAN PROVINCE, VIETNAM

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Abstract
Nui Chua National Park, Ninh Thuan province, has a semi-arid climate while locating right

next to a tropical forest climate, therefore, it has a rich biodiversity ecosystem, where the
coastal dry forest ecosystem is rarely seen in Vietnam. This area contains many valuable
geomorphologic features in denuded - lithological - tectonic terrain, among them, three features
can be considered as national treasures: 1) Nui Chua dome - block mountains; 2) Rai Cave
tectonic - abrasive coastline and 3) Lang Choi Stone Park. Fault-block Nui Chua Mountains is
the unique geomorphosite of Vietnam which has the right conditions for the dry ecosystem to
develop. The tectonic - abrasive coastline of Rai Cave and Lang Choi Rock Park is home to
unique and precious geoheritages such as two-stage development of boulders or balanced
rocks, karren sculpturing, caves, notches on ancient coral reefs terrace or spheroidal
weathering, tafoni on intrusive rocks, to name a few. To archive the goal of sustainable
development, it is important to link the conservation activities of the biodiversity at Nui Chua
National Park to the preservation efforts of geological diversity (geology, geomorphology) in
the area. Providing scientific explanations at each geomorphosites together with safe
sightseeing guides will help increase the quality of tourism, attract more visitors to explore and
learn about this mysterious, wonderful, and diverse ecosystem.
Keywords: geomorphosites, denuded - lithological - tectonic terrain, Nui Chua National Park,
Ninh Thuan province
Introduction
The term "geomorphosites", often used to refer to geomorphological heritage, is the
abbreviation of "geomorphological sites" (Panizza, 2001; Pralong, 2005). Compared with
geological heritages, geomorphologic heritage has three specific main characteristics:
aesthetics, dynamics, and overlap in scale (Reynard, 2009). The above three characteristics
mean these geoheritages are beautiful, active landforms, and vary in area from small to large.
These features make the geomorphologic heritage unique and attract visitors to admire and
explore. Over the past three decades, scientific studies have been carried out in many parts of
the world, focusing on the scientific and complementary values of the geological and
geomorphological heritages (Brilha, 2016; Fuertes-Gutiérrez and Fernández-Martínez, 2012;
Mihai Ielenicz, 2009; Nickolas C. Zouros, 2007). Like other geological heritages,
geomorphologic heritages deserve to be protected and preserved to pass on to future
generations.

Nui Chua National Park area has the driest climate in Vietnam, and has rich biodiversity both
in mountainous and coastal areas. Major tourist attractions within the Nui Chua National Park
such as Vinh Hy Bay, Rai Cave, Chua Mountains, and so on, can be considered as
geomorphosites (Figure 1).
Although Nui Chua National Park has been open for visitors for a long time, these tourist
attractions have not been extensively studied in terms of scientific and complementary values.
As a consequence, these geomorphosites still face problems with attracting a variety of visitors
as well as long-term solutions for protection and conservation.
Within this work, the scientific and additional values of geomorphosites in Nui Chua National
Park are investigated and presented. This valuable information of these heritages would help
to attract not only more visitors but also students and scientists to perform more thorough
investigation about this National Park
Methods

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The research is conducted based on the inventory of geomorphosites, followed the guideline of
Reynard et al., 2016, 2007 as steps below:
(1)Literature review about geology and geomorphology in journals, books, and the Vietnam
geological - mineral map, Da Lat - Cam Ranh, 1:200,000 scale (Vietnam Department of
Geology and Minerals, 1998).
(2)Potential sites were chosen to fieldwork for the detailed descriptions of each site included:

location, information on geology and geomorphology, accessibility, present uses and
infrastructure, protection, condition of the outcrop (visibility), other information (ecological,
cultural, historical, economic values) and photographic documentation.
(3)The preliminary assessment was conducted to pick out sites that have scientific and
additional values following the criteria proposed by Reynard. The scientific values consist of
four criteria: representativeness, unique/rareness, integrity and paleogeographical value
(detailed explanation and references of these criteria are shown in Table 1); the additional
values include three main criteria: ecology, aesthetics (viewpoints, contrasts, vertical
development, and space structuration), and culture (religious, historical, artistic, literary,
geohistorical, and economic importance). In this step, we chose 12 sites that have values to be
geomorphosites in this study area.
(4) The heritages are classified according to three levels: local (Ninh Thuan province), regional
(South Central coast of Vietnam), and national (Vietnam): based on the representativeness
or/and rareness of site in each scale. Besides that, we consider other scientific and additional
values to suggest the level of geomorphosites.

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Table 1. The scientific value of geomorphosite
Criterion
Scientific value
Representativeness A selected geomorphosite
should represent the most
complete and expressive
manifestation of a
geomorphological
phenomenon or a spatialgenetic pattern.

Concerns the rarity of the site
with respect to a reference
space.
This criterion of a site can
depend on different
indicators: on quantitative
parameters, or on qualitative
parameters; on spatialtemporal indicators.
State of conservation of the
site.

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Rareness/ Unique

Integrity

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Palaeogeographical
value

Importance of the site for the
Earth or climate history

Example in research area
Da Chong inselberg is 86 m high
mountain. It has many large rounded

granite boulders which precariously
balanced on top of another. This site
is representative for the balanced
rocks in the study area and the
South-Central Coast of Vietnam also.
Thit Beach is quite different from
other beaches in this region because
of its good conditions for sea turtles
spawning. The rareness of the sandy
beach is the highest value of this site.

Most of the sites in this area belong
to national park, therefore, they are
protected. by management boards.
Hon Do Cape has an ancient coral
reef terrace. The 4 – 5 m high marine
terrace represented the Quaternary
tectonics and East sea level changing
activities.

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(According to Brilha, 2016; Nickolas C. Zouros, 2007; Pereira and Pereira, 2010; Pralong,
2005; Reynard et al., 2016, 2007; Wimbledon W.A.P. et al., 2000).

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Research area
Nui Chua National Park locates in the Northeastern part of Ninh Thuan province. The national
park borders the Cam Ranh Bay - Khanh Hoa on the north, the East Sea on the east, Ninh Hai
district on the south, and the highway 1A on the southeast. Nui Chua National Park includes
Ninh Hai district, about a quarter of Thuan Bac district in Ninh Thuan province with an area
of 29.856 ha, of which 22.513 ha is land, 7.352 ha is the sea. Two roads with easy access to the
geomorphological features are the national highway 1A and the provincial road 702. Besides,
the North-South railway, which runs parallel to the national highway 1A and the sea, is another
convenient transportation method to visit the national park.

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Figure 1. Geological map of Nui Chua National Park (modified from Vietnam Department
of Geology and Minerals, 1998)
Geology and geomorphology
The Cretaceous Deo Ca intrusive complex occupies most of the studied area and has the Da
Lat Late Mesozoic active continental margin structure (Tran Van Tri and Vu Khuc, 2009). The
main intrusive rock are granite, granosyenite, and granodiorite (Nguyen Duc Thang, 1999).
Nui Chua Mountain is composed of intrusive rocks with six peaks. Among those, the highest

is Co Tuy (1,039m), also known as Chua Anh Mountain (means older brother). The 5 other
peaks are named Chua Chong Mountain (means husband), Chua Vo Mountain (means wife),
Chua Em Mountain (means younger brother), Chua Chau Mountain (means grandchild), and

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Chua Chat Mountain (means great-grandchild). Holocene marine sediments occupy only a
small area in the south and include sand, gravel, coral debris, and coral reefs. These
sedimentsform a 4 – 5 m high marine terrace, which is equivalent to the Ca Na terrace that was
formed in the Flandrian transgression stage (Le Duc An, 2012). Orthogonal joint systems
included two vertical systems dominantly in the direction 1) NE-SW, NW-SE and 2) sublongitude, sub-latitude and horizontal system. The processes of denudation were developed
according to the joint systems that cut into the intrusive rock bed, which were the basis for
forming the typical boulder of the area.

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Climate and hydrography
According to “Köppen-Geiger Climate Classification” the study area belongs to the tropical
savanna climate entirely (Kottek et al., 2006). Ninh Thuan province has two distinct seasons:
the rainy season from September to December and the dry season from January to August. The
average temperature ranges from 24.6 to 27.2 C. There is a distinct dry season, where there
will be no rain for months. Then a short rainy season brings heavy rains mostly in the
afternoons, with hot, humid conditions throughout the rest of the day. Even with the rainy
season, the annual rainfall is the lowest rainfall in South-Central Vietnam (430-940 mm), while
the evaporation is quite high (1295.8-2210.1 mm), twice as much as the rainfall (Tu Thi Nam
et al., 2018). The streams and springs in the national park are narrow, seasonal flow from the
Nui Chua Mountain into the sea. Most of the streams dry up during the dry season. The tidal
patterns that occur along the Ninh Hai district coastline are irregular diurnal tides. The average
amplitude of tides is about 0.8-1.2 m, with the highest is over 1.5 m (Pham Ngoc Quy et al.,
2011). From January to April, the prevailing winds blow southwest, the average wave height
is 1.0-1.1 m with the maximum is about 2.0 m. From October to December, winds prevail from
the Northeast, the average wave height is about 1.2 m and the maximum is about 2.5 m. The
studied area is located in Ninh Thuan - Bac Binh Thuan upwelling zone, which occurs from
June to September. Upwelling brings nutrients into the surface water of the ocean, results in
some of the most productive marine ecosystems (Nguyen Kim Vinh, 2007).
Ecology:
Nui Chua National Park is located in the driest part of Vietnam therefore it has the typical and
unique dry forest ecosystems rarely seen in Vietnam and Southeast Asia. According to Duc et
al., 2009, the only primary forest that remains is evergreen forest at elevations > 700 m above
sea level in the north of the park. Below 700 m above sea level, on the east side of the mountains
there are large areas of four types of secondary forest such as sclerophyll evergreen forests, dry
deciduous forest and tropical savanna woodland, dry thorny scrub and thorny woodland; thorny
scrubland (Duc et al., 2009).
Nui Chua National Park has 1,504 vascular plant species. In terms of fauna, it currently has

306 species of animal, of which 64 are rare and conserved species (Tran Van Tiep and Dang
Thi Thanh Thuy, 2014). There are several species such as Red-shanked Douc Langur
(Pygathrix nemaeus) was listed in the Red List of IUCN as Endangered Asian colobine monkey
(Craig Hilton-Taylor (Compiler), 2000). The coastal reefs are in relatively good condition,
including 310 species (Si Tuan Vo et al., 2014). In addition, Nui Chua National Park is one of
the rare inland spawning beaches for sea turtles ((Tran Van Tiep and Dang Thi Thanh Thuy,
2014).
Results and discussion
Geomorphosites
Conducting inventories and field surveys, we identified 12 geomorphosites which can be
classified into five types: (1) mountains, (2) bays and lagoons, (3) marine terraces, (4) rocky
coastline, and (5) beaches. The scientific and additional values are shown in Figure 2 and
summarized in Table 2.

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The common geomorphosites are balanced rocks (which are composed of two or more
boulders, perched one on the other (Twidale and Vidal Romaní, 2005)) in denuded products of
which dominant factors are orthogonal joints system and homogeneous material of intrusive
rock bodies. These can be called denuded - lithological – tectonic terrain in mountainous areas
and abrasive – lithological – tectonic terrain in lower coastal areas. In addition, the system of
fractures is oriented to extend the coastline, currents, bays, and lagoons.

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Figure 2. Geomorphosites of Nui Chua National Park - Ninh Thuan provinceTable 2. Summary of scientific value and additional value of
geomorphosites in Nui Chua National Park - Ninh Thuan

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