Prelude: What is Geology?

Nature of the scientific method

- Class discussion

Overview of Earth Systems

Origin of the Earth and Solar System

Nebular hypothesis

Today: Lecture OverviewToday: Lecture OverviewToday: Lecture OverviewToday: Lecture Overview

http://http://geologygeology.asu.edu/jfarmer/g_stu_1.html.asu.edu/jfarmer/g_stu_1.html

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““And just what is Geology?”And just what is Geology?”

Prelude:Prelude:

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

Hotter stuff is lighter and risesCooler stuff is denser and sinks.

Prelude:Prelude: Earth’s internal structure

crust

mantle

core

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

Upper 34-670 kmLower 670-2900 km

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

3 distinct divisions:

Earth’s dynamic interior and crust

Heat loss drives plate tectonics

Three types of plate boundaries

Prelude: Plate TectonicsPrelude: Plate TectonicsPrelude: Plate TectonicsPrelude: Plate Tectonics

Prelude: Earth Systems

Solid Earth

Atmosphere

Hydrosphere

Cryosphere

Biosphere

AtmosphereAtmosphere

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

Blanket of gases surrounding the EarthBlanket of gases surrounding the Earth

HydrosphereHydrosphere

Oceans (most prominent) 71% of surface of Earth

Streams, lakes, glaciers, underground water

Atmosphere

Water portion of EarthWater portion of Earth

CryosphereCryosphere

Glaciers

Permafrost and ground ice

Polar ice caps

Frozen polar seas

Icy portion of Earth’s crustIcy portion of Earth’s crust

Water is the primary agent of crustal weathering

BiosphereBiosphere

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’s EcosystemsEarth’s Ecosystems

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 PlantsPlants 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.

LichensMycorrhizae

Credit: Sharnoff

Credit: INVAM

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

Earth is one of nine planets comprising the Solar System

How did the Solar System form?

Earth FormationEarth 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.