UNIT 1: EARTH SYSTEMSEnvironmental Science

Connection• The Earth as a System:

• The Earth consists of rock, air, water, and living things that all interact with each other.

• Scientists divide this system into 4 parts:• Geosphere (rock)• Atmosphere (air)• Hydrosphere (water)• Biosphere (living things)

Geosphere• The geosphere is the solid part of the Earth.• Consists of all rock (solid and liquid) as well as soils and

dirt.• Most of the geosphere is in the Earth’s interior.

• At the equator, the average distance through the center of the Earth to the other side is 12,756 km (~8,000 miles)

Geosphere: Earth’s Interior• Scientists use seismic waves to study the interior of the

Earth. (Waves produced by an earthquake)• Deepest well ~12 km (9 miles).• Waves travel at different speeds depending on the density of

material.• This has allowed scientists to infer what substances make up the

interior of the Earth.

Earth’s Composition

•Scientists divide the Earth into 3 layers:•Crust •Mantle•Core

Crust• Outermost layer• Composed of lighter weight elements• 5-70 km thick• Makes up less than 1% of Earth’s total mass• Also known as lithosphere

Mantle• Layer between crust and core• Liquid rock• Composed of dense, iron-rich minerals (medium density)• ~ 2,900 km thick• Makes up ~ 64% of Earth’s total mass• Composed of 2 layers

• Asthenosphere: plastic-like layer of liquid rock that flows very slowly (allows tectonic plates to move on top of it)

• Mesosphere: lower level mantle. Convection currents cause movement of a-sphere

Core• Innermost layer• Composed of densest elements (nickel and iron)• 2 layers

• Outer core (liquid)• Inner core (solid)

Plate Tectonics• The Earth’s crust (lithosphere) is broken into pieces called

tectonic plates.• Plate Boundaries:

• Collide (form mountains/trenches)• Separate (form new crust)• Slide (earthquakes)

Volcanoes• Mountains built from magma (liquid rock) that rises from

Earth’s interior.• On land• Under ocean (volcanic islands)

• Ring of Fire: String of volcanoes along the boundary of the Pacific plate.

Erosion• Forces at plate boundaries bring rock to Earth’s surface.• Rock is continuously effected/shaped by erosion.

• Removal of rock particles by a moving force (water/wind)

Atmosphere• The atmosphere is the mixture of gases that makes up

the air we breathe.• Almost all of these gases are found in the first 30 km

above the surface of the Earth.• Approximately 78% of the atmosphere is nitrogen, 21% is oxygen,

and the remaining % is a mixture of water vapor, CO2, and all other gases.

The Atmosphere• The atmosphere is the mixture of gases that surround the

Earth.• Composition is constantly changing as gases are added/removed

by different systems (living and non-living).

Layers of the Atmosphere• 4 layers based on temperature changes at different

distances above the Earth’s surface.• Troposphere (closest/densest: almost all weather occurs,

temperature decreases as altitude increases.)• Stratosphere (2nd: temperature increases as altitude increases b/c

of the ozone absorbing UV energy and warming the air.)• Mesosphere (3rd: coldest layer, recorded at -93oC.)• Thermosphere (Outermost: Nitrogen and Oxygen absorb solar

radiation resulting in temps above 2,000oC)

Northern Lights (aurora borealis)• Lower thermosphere absorbs harmful solar radiation (x-

rays and gamma rays)• Causes atoms to become electrically charged (ions)

• Ions sometimes radiate energy as light (seen near North and South poles.)

Energy in the Atmosphere• Energy is transferred by 3 mechanisms:

• Radiation: transfer of heat across space• Conduction: transfer by direct physical contact• Convection: transfer by currents (hot rises/cool sinks)

• The movement of hot/cool air in the troposphere is what causes weather.

• Our planet only receives about two-billionths (0.000000002 %) of the energy put out by the sun.

The Greenhouse Effect• The gases in the atmosphere can act like the windows of

a greenhouse.• Sunlight heats the surface of the Earth • Heat radiates back into the atmosphere • More gets trapped by the greenhouse gases in the

atmosphere causing gradual increase in global temperatures (global warming)

• Greenhouse gases:• Carbon dioxide• Water vapor• Methane

Hydrosphere• The hydrosphere makes up all the water on or near the

surface of the Earth.• Most is found in the oceans.• Water is in the atmosphere and on land as well.

Water Cycle Review• The hydrosphere includes all of the water on or near the

surface of Earth.• The water cycle is the continuous movement of water into

the air, onto land, and then back to water sources.• The major processes of the water cycle include:

• Evaporation: liquid water heated and turned into water vapor that rises into the atmosphere.

• Condensation: water vapor forms droplets on dust particles (clouds)• Precipitation: droplets fall back to Earth (rain/sleet/snow/hail)

The Oceans• The world ocean (all oceans are connected) 70% of the

Earth.• Pacific • Atlantic• Indian• Arctic• Southern

Oceans Cont.• The difference between fresh water and ocean water is

that it contains more salts.• Dissolved out of rocks on land and carried to the oceans by rivers,

and underwater volcanic eruptions add to the salt content.• Salinity is the concentration of salts in water.

Ocean Currents• Currents are stream-like movements of water in the

ocean.• Surface currents• Deep currents

• Ocean currents can effect temperature and weather all around the world.• Northern hemisphere = clockwise• Southern hemisphere = counter clockwise

Freshwater• ~ 3% of all water on Earth is freshwater.• River system: a network of streams that drains and area

of land.• Tributaries: smaller streams/rivers that flow into larger ones.

• Groundwater: most water trickles through rock and collects underground• Aquifer: layer of rock that allows groundwater to flow• Fulfills drinking needs of humans

Biosphere• The biosphere is made up of parts of the other 3 spheres.

• Where all life exists.

• Thin layer that extends from about 9 km above the Earth’s surface down to the bottom of the ocean.