Earth systems

Today: Lecture Overview
Prelude: What is Geology?
Nature of the scientific method
- Class discussion
Overview of Earth Systems
Origin of the Earth and Solar System
Nebular hypothesis


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Prelude:

“And just what is Geology?”


Solid Earth

Interior of the
Earth is losing
heat.
Primary source
of heat:
Radioactive decay
Heat loss drives
convection, based
on density
differences

Hotter stuff is
lighter and rises
Cooler stuff is
denser and sinks.


Prelude: Earth’s internal structure

3 distinct divisions:
crust

Oceanic 0-6 km (“young”, < 180 m.y.)
Continental 0-34 km (older, up to 3.8 b.y.)

mantle

Upper 34-670 km
Lower 670-2900 km

core

Outer (liquid) 2900-5160 km
Inner (solid) 5160-6370 km


Prelude: Plate Tectonics

Earth’s dynamic interior and crust
Heat loss drives plate tectonics
Three types of plate boundaries

Prelude: Earth Systems
Solid Earth

Atmosphere

Hydrosphere

Cryosphere

Biosphere


Atmosphere
Blanket of gases surrounding the Earth

Protection from Sun’s heat & UV rays
Weather: due to exchange of energy
between Earth’s surface & atmosph.
between atmosph. & outer space
Strongly interacts w/ surface


Hydrosphere
Water portion of Earth
Oceans (most prominent)
71% of surface of Earth
Streams, lakes, glaciers, underground water
Atmosphere

Cryosphere
Icy portion of Earth’s crust

Glaciers
Permafrost and ground ice
Polar ice caps
Frozen polar seas


Water is the primary agent of crustal weathering


Biosphere
Earth’s Ecosystems

Earth’s biosphere occupies both the surface and
subsurface to depths of a few kilometers
Life occupies an extreme range of environments
Life strongly interacts with the atmosphere, the
hydrosphere and the solid earth to affect their
composition and long-term evolution (these
interactions are called ecology!)


Earth: The Living Planet


Most of the biodiversity on our planet is microbial!

The Three Domains of Life


Boiling mudpot, Yellowstone

Some extremes of life


Fungi and Plants
Plants consume carbon dioxide and produce oxygen
via photosynthesis. Most of the 21% oxygen in our
atmosphere derives from this process!
Fungi and and plants form symbioses called Lichens and
Mycorrhizae that alter rocks and produce soils.
Lichens

Mycorrhizae

Credit: INVAM

Credit: Sharnoff




Against a constant backdrop of gravity,
the atmosphere, hydrosphere and
biosphere interact with the rocks of the

Earth’s crust to break them down and
transport them to depositional basins
(e.g. the oceans) as sediment. The cycle is
renewed as internal processes of plate
tectonics create new crust and uplift
it to form mountain ranges.


Earth is one of nine planets comprising the Solar System

Earth
How did the Solar System form?


Earth Formation
Planets thought to
have formed:
At same time
From same
material as the
Sun

Nebular hypothesis
Solar system formed from giant cloud of mostly
hydrogen and helium, and a small percentage of heavier
elements.


Nebular Hypothesis:
States that the planets of

our Solar System were
formed by the “accretion”
of materials from a cloud
of gas and dust
called a solar “nebula”.
Collapse of the nebula under
its own gravity formed a
rotating disk around
a dense, central core of
material. This core
eventually became hot
enough to form the Sun.