2. Earth Layers

The Four Great Realms

Lithosphere - processes associated with the solid earthHydrosphere - processes associated with waterAtmosphere - processes associated with the gases that envelope the earthBiosphere - processes that involve living organisms

Inside the Earth

Lithosphere

Origin• Cooling off and

solidification

• Thermal convection currents

Present• Consists of soil, rocks

and minerals

• Contains landforms– Hills, mountains, valleys

• Temperature increases up to 15C/km deep

Composition

• Crust

• Mantle

• Core

The Crust

• Outer layer• 5-100 km thick• temperature ranges

between 10 to 20C/km deep

• 2 types of crust– Oceanic (very dense,

made of basalt)– Continental (less

dense, made of granite)

Oceanic and Continental Crust

Types of Crust

Continental• Predominantly granitic

• Granite or sialic rock--- richer in aluminum and silicon

Oceanic• Basaltic

• Basalt or simatic rock---richer in magnesium and silicon

The Mantle

• Middle layer• Very thick layer• Temperature at the

core-mantle boundary 3000C

The Core• Made mostly of iron

• 1/3 of the earth’s mass

• Very hot about 4000C

Earth’s Layers

• How are the earth’s layers similar to an egg?

• Shell=crust• Egg white=mantle• Yolk=core

Physical Structure of the Earth(5 Layers)

• Lithosphere- rigid outer layer (crust)

• Asthenosphere- solid rock that flows slowly (like hot asphalt)

• Mesosphere- middle layer

• Outer Core- liquid layer

• Inner Core- solid, very dense

Tectonic Plates• Earth’s crust is broken into about 19

pieces

• These plates move on top of the asthenosphere

Atmosphere

The earth’s life giving blanket

Origin of the Atmosphere

• Volcanic Eruptions• Extensive period of

global volcanic activity

• Reducing atmosphere

The present atmosphere

• Air: invisible, odorless mixture of gases and suspended particles

• Aerosols• Water vapor

Layers of the atmosphere

• 4 layers• troposphere,

mesosphere, thermosphere stratosphere

Troposphere

• the layer that is closest to the surface of the earth

• It’s elevation ranges from 0 to 10 km

Stratosphere

• sits on top of the troposphere

• It’s elevation ranges from 10 km to around 25 km

• contains the ozone layer, which protects us from harmful sunlight

Mesosphere

• Middle layer above the stratosphere

• It’s elevation ranges from 25 to 100 km

• Temperature diminishes with altitude

• Minimu tepmt is about -80C

Thermosphere

• highest layer of the atmosphere

• It’s height ranges from 100 to 400 km

• where most small meteorites burn up

• Temperature is very high• the location in the

atmosphere that the northern lights occur (aurora borealis)

Composition of Air

• There are many different types of gasses in the atmosphere

• They include nitrogen, oxygen, argon, carbon dioxide and other noble gasses

• The gas that is most abundant is nitrogen

Hydrosphere

• Liquid part of the earth– oceans– ice caps– lakes– rivers– underground aquifers– soil water– atmosphere– living organisms

Hydrosphere

Origin

• Occasional raindrops

• Global deluge of rains

• Formation of oceans, rivers, lakes and underground water tables

Present

• Moving, dynamic mass of liquid

• Solar energy drives hydrologic cycles

• Essential for life: univesal solvent

Earth’s water budget - water cycle

– 97.4% salt water - only 2.6% fresh water– Of that 2.6%, over 80% is in ice caps &

glaciers– 0.59% is in ground water– <0.001% in atmosphere

• Remainder in lakes, soil water, rivers and organisms (in decreasing order of storage)

Global Hydrologic Cycle(key component of the global climate

system)

Freshwater as a resource

• Renewable through evaporation from the seas and precipitation (solar powered)

• Demands for freshwater include:– Human consumption (10%)– Irrigation (70%)– Industry (20%)

• Demands increase with increasing population

• Unequal distribution of freshwater

Human impacts on water cycle

• Global warming - may disrupt rainfall patterns

• Withdrawing of ground water faster than it can be replenished

• Pollution• Deforestation• Increased demand• Inequity of use

Sustainable use of freshwater

• Methods of increasing freshwater supply– Rain barrels– Dams and reservoirs– Water purification– Desalination ($3/4,000L)– Storm water management

Summary

• From the atmosphere came the hydrosphere, just as the atmosphere came from the lithosphere

• For about 2 BY, the 3 spheres interacted • And from the interaction, about 4BY

evolved the biosphere