Unit 2: The Earth System Atmosphere, Hydrosphere & Geosphere.

Unit 2: The Earth SystemUnit 2: The Earth System

Atmosphere, Hydrosphere & Atmosphere, Hydrosphere & GeosphereGeosphere

Function, Composition and Structure of the Atmosphere

Functions• Air we breath, plants use in photosynthesis• Filters solar energy, blocking much of harmful

UV wavelengths• Protects us from “space junk”• Allows for a natural greenhouse effect keeping

earth warm enough for liquid water and life• Cycles moisture and heat throughout earth in

moving air systems providing weather patterns and the water cycle

• weathers and shapes earth’s surface, allowing the rock cycle

Composition of Today’s Atmosphere

• Variable components:• Water (0-4%)• Dust, ozone, pollution

Compare to neighbors

Structure of Atmosphere

– Gas molecules thin with altitude

– What holds them near earth’s surface?

Atmosphere blends to Exosphere

Heating the Atmosphere

• Troposphere=heated by terrestrial radiation

• Stratosphere& Mesosphere=absorption and re-radiation of shortwave radiation in the ozone layer

• Thermosphere=absorption and re-radiation of shortwave radiation by oxygen

Evolution of the Atmosphere

1. Loss of original atmosphere due to solar wind

2. Formation of early atmosphere by outgassing

3. Evolution of atmosphere by interactions with biosphere, hydrosphere, and geosphere

4. Today’s atmosphere5. Human’s effect on today’s atmosphere

Solar wind• 1 million tons of matter out into space

every second!

• 95% protons or H+ ions, plasma state

Solar wind is different than earth wind

• Not as dense• Plasma vs.

gas

Solar Wind wipes early atmosphere away

• When sun first began to shine, early atmosphere in inner solar system blown out past the asteroid belt where it was cooler

• Only dense materials with very high melting points able to remain (rocky, metallic elements)

Outgassing• Gases from volcanoes

– water vapor (H2O), – carbon monoxide (CO), – carbon dioxide (CO2), – hydrochloric acid (HCl), – methane (CH4), – ammonia (NH3), – nitrogen (N2),– sulfur gases. – no free oxygen

• Additions to atmosphere: perhaps from comets?

Evidence for composition of early atmosphere

• Today’s volcanic eruptions• Rocks from early earth history• Early organisms are anaerobic (cannot survive in

O2)

Banded Iron Formation

• not present in rocks younger than 1.8 - 2.5 billions of years ago, when oxygen starting becoming more abundant.

• Alternating layers of magnetite, hematite (iron oxide) and silica-rich minerals

• Struggle between

oxygen-rich and oxygen-poor

environment

The Oxygen explosion

• The amount of oxygen increased due to early life forms, such as cyanobacteria that produce oxygen as a waste product

• Water vapor split by incoming solar radiation into hydrogen and oxygen, hydrogen escapes

Role of the Oceans

• Environment for early life

• Absorption of carbon dioxide and other toxic gases

Consequences of Oxygen Build-up

• Development of ozone (O3) layer which absorbs harmful UV radiation and eventaully allowed life on land

• End of banded iron formations which only formed in low O2

• Oxygen breathing organisms evolved

Composition, function, structure of Hydrosphere

Function & Significance of Hydrosphere

• Necessary for the evolution and the abundance of life

• Helps circulate heat

• Absorbs and facilitates the storage of carbon dioxide allowing earth to develop and maintain low CO2 levels

Structure and Composition

• All water on earth recycles between reservoirs

• Most freshwater is in the ground, some in lakes and rivers, atmosphere

Water Cycle

Water: changes of state

Evolution of the Hydrosphere1. Outgassing (& perhaps comets) adds

water vapor to atmosphere2. Saturated atmosphere causes great

rains3. Great rains cool surface and collect in

massive freshwater ocean4. Landmasses weather and running water

carries dissolved material (salts) to the ocean

5. Water cycle, driven by sun, continues to cycle water today

Great Rains

Ocean getting salty

• Weathering of rocks

• Undersea volcanoes and vents

• Balance of salt, not getting saltier

Composition, Structure, & Function of Geosphere

Function & Significance of Geosphere

• Storage of most of earth’s matter• Volcanic activity responsible for

atmosphere, climate changes, new crust• Plate movements causing crust to be

recycled including elements that accumulate such as carbon and “salt”

• Provides varied topography on which both dry and wet land creatures dwell

• Weathers to form soil from which land plants derive many nutrients

Evolution of Geosphere1. Solid rock, metal and ice accrete to form

protoplanet from solar nebula

2. Gravitational compression & impacts cause early earth to become molten

3. Differentiation based on density formed layers out of molten earth, gasses escaped.

4. Great collision causes large chunk of crustal rock to rip away & form moon. Gravity pulls both back into molten spheres

Earth’s Layered Structure

Evolution of Geosphere cont.

5. Crust cools but heat from within causes eruptions of rock and gas to continue, also causes plates to shift

6. Plate collisions and volcanic activity create landmasses above sea level

7. Heat within drives plate motions causing landmasses to shift and rocks to recycle

8. Interaction between weathering and uplift create today’s landscape

Plate Tectonics

Rock Cycle

What is the geopshere made of?

• Common elements

• Elements make up minerals

• Rocks are made of minerals

3 main types of rocks

• Based on formation• Igneous=• Sedimentary=• Metamorphic=• Common

characteristics of each

Rodinia

Gondwana

Brr…

Oceans begin to close

Pangea is forming, Appalachians

Greatest extinction (99%) of all time!

Pangea breaks up

Major Extinction

Himalayas form

Most recent Ice age

Today

• http://www.ucmp.berkeley.edu/help/timeform.html Great site to get overview of events in each time period and dates

• http://www.scotese.com/earth.htm (good for geology and climate)

• http://www.pbs.org/wgbh/nova/ice/chill.html ice ages