ENVIRONMENTAL SCIENCEENVIRONMENTAL SCIENCE

Chapter 3 The Dynamic EarthChapter 3 The Dynamic Earth3.1 The Geosphere3.1 The Geosphere

3.1 The Geosphere 3.1 The Geosphere ObjectivesObjectives• Describe the composition and structure of Describe the composition and structure of

the Earth.the Earth.• Describe the Earth’s tectonic plates.Describe the Earth’s tectonic plates.• Explain the main cause of earthquakes Explain the main cause of earthquakes

and their effects.and their effects.• Identify the relationship between volcanic Identify the relationship between volcanic

eruptions and climate change.eruptions and climate change.• Describe how wind and water alter the Describe how wind and water alter the

Earth’s surface.Earth’s surface.

The Earth as a SystemThe Earth as a System• The Earth is an integrated system made of The Earth is an integrated system made of

four major systems that constantly interact four major systems that constantly interact and affect one another.and affect one another.– Geosphere – solid part of Earth, the rocks, soil, Geosphere – solid part of Earth, the rocks, soil,

and sedimentand sediment– Atmosphere – envelope of gases that surround Atmosphere – envelope of gases that surround

the Earththe Earth– Hydrosphere – all of the water on EarthHydrosphere – all of the water on Earth– Biosphere – all of the living things (organisms) Biosphere – all of the living things (organisms)

on Earthon Earth

The Earth as a SystemThe Earth as a System• The majority of the geosphere is located beneath The majority of the geosphere is located beneath

the surface of the Earth.the surface of the Earth.• The average diameter of the Earth at the equator The average diameter of the Earth at the equator

is 12,756 km.is 12,756 km.• Most of the molecules that make up the Most of the molecules that make up the

atmosphere are found in the lower 30 km of our atmosphere are found in the lower 30 km of our atmosphere.atmosphere.

• Oceans cover about 71% of the Earth’s surface.Oceans cover about 71% of the Earth’s surface.• The life, or biosphere can be found living from the The life, or biosphere can be found living from the

bottom of the ocean to about 9 km above sea bottom of the ocean to about 9 km above sea level – a total range of about 20 km.level – a total range of about 20 km.

Discovering Earth’s InteriorDiscovering Earth’s Interior• The Earth’s interior cannot be studied The Earth’s interior cannot be studied

through direct observation – the deepest through direct observation – the deepest well drilled is only about 12 km deep.well drilled is only about 12 km deep.

• Scientists use seismic waves to study the Scientists use seismic waves to study the structure of the Earth’s interior.structure of the Earth’s interior.

• A seismic wave is altered by the material A seismic wave is altered by the material through which it travels.through which it travels.

• Seismologists measure the speed and Seismologists measure the speed and direction of seismic waves as they direction of seismic waves as they penetrate the Earth’s interior.penetrate the Earth’s interior.

Discovering Earth’s InteriorDiscovering Earth’s Interior• The Earth can be divided into three The Earth can be divided into three

compositional layers.compositional layers.– CrustCrust– MantleMantle– CoreCore

• These layers are made with These layers are made with progressively denser material closer progressively denser material closer to the Earth’s center.to the Earth’s center.

Discovering Earth’s InteriorDiscovering Earth’s Interior• The crust is a thin, outer layer of the The crust is a thin, outer layer of the

Earth made almost entirely of lighter Earth made almost entirely of lighter elements.elements.

• The crust makes up less than 1% of The crust makes up less than 1% of Earth’s mass.Earth’s mass.

• Oceanic crust is 5 km to 8 km thick and Oceanic crust is 5 km to 8 km thick and made mostly of basalt.made mostly of basalt.

• Continental crust, mostly granite based, Continental crust, mostly granite based, is between 20 km to 70 km thick.is between 20 km to 70 km thick.

Discovering Earth’s InteriorDiscovering Earth’s Interior• The mantle, just below the crust, makes The mantle, just below the crust, makes

up 64% of the mass of the Earth.up 64% of the mass of the Earth.• The mantle is about 2,900 km thick and The mantle is about 2,900 km thick and

is made mostly of medium density rock.is made mostly of medium density rock.• The core, Earth’s inner-most layer, is The core, Earth’s inner-most layer, is

composed of the densest elements and composed of the densest elements and has a radius of about 3,400 km.has a radius of about 3,400 km.

Discovering Earth’s InteriorDiscovering Earth’s Interior• The Earth, based on physical properties, can be The Earth, based on physical properties, can be

divided into five layers.divided into five layers.– Lithosphere (15 to 300 km thick) a cool, rigid layer that Lithosphere (15 to 300 km thick) a cool, rigid layer that

includes the crust and the upper part of the mantle and includes the crust and the upper part of the mantle and is divided into large tectonic platesis divided into large tectonic plates

– The asthenosphere (250 km thick) is a plastic, solid layer The asthenosphere (250 km thick) is a plastic, solid layer of the mantle that flows very slowly and allows tectonic of the mantle that flows very slowly and allows tectonic plates to move on top of itplates to move on top of it

– Mesosphere – (2,550 km thick) the lower layer of the Mesosphere – (2,550 km thick) the lower layer of the mantle between the asthenosphere and the outer coremantle between the asthenosphere and the outer core

– Outer core (2,200 km thick) outer shell of Earth’s core Outer core (2,200 km thick) outer shell of Earth’s core made of liquid nickel and ironmade of liquid nickel and iron

– Inner core – (1,228 km radius) sphere of solid nickel and Inner core – (1,228 km radius) sphere of solid nickel and iron at the Earth’s centeriron at the Earth’s center

Plate TectonicsPlate Tectonics• The Earth’s lithosphere is divided into large tectonic The Earth’s lithosphere is divided into large tectonic

plates which glide across the underlying plates which glide across the underlying asthenosphere much like chunks of ice setting on a asthenosphere much like chunks of ice setting on a frozen lake.frozen lake.

• The continents are located on tectonic plates and The continents are located on tectonic plates and move around with them over time.move around with them over time.

• Much of the geologic activity that occurs at the Much of the geologic activity that occurs at the Earth’s surface takes place at tectonic plate Earth’s surface takes place at tectonic plate boundaries.boundaries.

• The formation of mountains and volcanoes, as well The formation of mountains and volcanoes, as well as violent earthquakes, are the result of the forces as violent earthquakes, are the result of the forces of tectonic activity.of tectonic activity.

Plate TectonicsPlate Tectonics• There are three There are three

types of plate types of plate boundaries.boundaries.– ConvergentConvergent

• Ocean – ocean Ocean – ocean collisioncollision

• Ocean – continent Ocean – continent collisioncollision

• Continent – Continent – continent collisioncontinent collision

– DivergentDivergent– TransformTransform

EarthquakesEarthquakes• A fault is a fracture in the bedrock along A fault is a fracture in the bedrock along

which movement has occurred.which movement has occurred.• When rocks are under stress along a When rocks are under stress along a

fracture, they can sometimes snap as the fracture, they can sometimes snap as the stress is released.stress is released.

• The vibrations which travel through the The vibrations which travel through the ground as a result of this release of energy ground as a result of this release of energy are known as earthquakes.are known as earthquakes.

• Earthquakes occur all the time, but most Earthquakes occur all the time, but most are not felt (only detected by are not felt (only detected by instrumentation).instrumentation).

EarthquakesEarthquakes• The amount of energy released by an The amount of energy released by an

earthquake can be quantified and earthquake can be quantified and compared on the Richter Scale.compared on the Richter Scale.

• The smallest magnitude that can be felt is The smallest magnitude that can be felt is 2.0 and the largest magnitude ever 2.0 and the largest magnitude ever recorded was 9.5.recorded was 9.5.

• An increase in magnitude of whole number An increase in magnitude of whole number indicates the release of 31.7 times more indicates the release of 31.7 times more energy than the number below it.energy than the number below it.

• The majority of earthquakes occur along The majority of earthquakes occur along plate margins.plate margins.

EarthquakesEarthquakes• Though earthquakes Though earthquakes

cannot be accurately cannot be accurately predicted, risk for predicted, risk for earthquakes can be earthquakes can be better assessed.better assessed.

• Earthquakes can Earthquakes can damage roads, gas damage roads, gas lines, electrical lines, electrical supply, sewage, and supply, sewage, and even large buildings.even large buildings.

VolcanoesVolcanoes• Volcanoes are mountains build from molten Volcanoes are mountains build from molten

rock (magma and lava) and are often rock (magma and lava) and are often located near tectonic plate boundaries.located near tectonic plate boundaries.

• Most of the world’s active volcanoes on Most of the world’s active volcanoes on land are located on tectonic plate land are located on tectonic plate boundaries that surround the Pacific Ocean.boundaries that surround the Pacific Ocean.

• Volcanic eruptions can be devastating Volcanic eruptions can be devastating locally with gas and pyroclastic flows that locally with gas and pyroclastic flows that can exceed 200 km/hr.can exceed 200 km/hr.

• Ash from eruptions can also be carried in Ash from eruptions can also be carried in the atmosphere and travel far.the atmosphere and travel far.

VolcanoesVolcanoes• Volcanic eruptions Volcanic eruptions

can alter global can alter global weather conditions.weather conditions.

• When Mt. St. When Mt. St. Helens erupted in Helens erupted in 1980, average 1980, average global temperature global temperature dropped slightly.dropped slightly.

ErosionErosion• The Earth’s surface is subject to the The Earth’s surface is subject to the

effects of weathering and erosion.effects of weathering and erosion.• Wind and water are constantly working to Wind and water are constantly working to

remove and transport surface materials.remove and transport surface materials.• Water erosion, over time, can dramatically Water erosion, over time, can dramatically

change the landscape.change the landscape.– For example, the Grand Canyon was created For example, the Grand Canyon was created

by stream erosion over timeby stream erosion over time• Wind erosion is most evident in desert and Wind erosion is most evident in desert and

beach areas.beach areas.

ReferencesReferences• Earth’s Compositional Layers - Earth’s Compositional Layers - http://www-http://www-

cms.llnl.gov/s-t/extreme_chemistry.htmlcms.llnl.gov/s-t/extreme_chemistry.html • Earth’s Structural Layers - Earth’s Structural Layers -

http://schoolscience.rice.edu/science/currichttp://schoolscience.rice.edu/science/curricula/printpreview-noimage.cfm?CurriculaIDula/printpreview-noimage.cfm?CurriculaID=315=315

• Earth Structure Compared - Earth Structure Compared - http://elmo.shore.ctc.edu/ebaer/Geology%http://elmo.shore.ctc.edu/ebaer/Geology%20101/tests/test1key.html20101/tests/test1key.html

• Tectonic Plates - Tectonic Plates - http://http://www.stchas.edu/faculty/ewilson/Photos/Plawww.stchas.edu/faculty/ewilson/Photos/Platestes

ReferencesReferences• Earthquake Distribution - Earthquake Distribution -

http://www.geology.uiuc.edu/~hsui/classes/geo11http://www.geology.uiuc.edu/~hsui/classes/geo116/lectures/earthquakes-demo.htm6/lectures/earthquakes-demo.htm

• Earthquake in San Francisco - Earthquake in San Francisco - http://www.geology.uiuc.edu/~hsui/classes/geo11http://www.geology.uiuc.edu/~hsui/classes/geo116/lectures/earthquakes-demo.htm6/lectures/earthquakes-demo.htm

• Tectonic Plate Boundaries - Tectonic Plate Boundaries - http://www.scarborough.k12.me.us/wis/teachers/dhttp://www.scarborough.k12.me.us/wis/teachers/dtewhey/webquest/nature/plate%20boundaries.httewhey/webquest/nature/plate%20boundaries.htmm

• Pyroclastic Flow - Pyroclastic Flow - http://www.geo.umn.edu/courses/1001/Summer_Shttp://www.geo.umn.edu/courses/1001/Summer_Session/SedImages.htmlession/SedImages.html

ReferencesReferences• Mt. St. Helens - Mt. St. Helens -

http://geosciences.ou.edu/~msoreg/volcanoehttp://geosciences.ou.edu/~msoreg/volcanoes/Mt_StHelens1.html s/Mt_StHelens1.html

• Death Valley Sand Dunes - Death Valley Sand Dunes - http://www.beachdoctor.com/sethmedlin/Fahttp://www.beachdoctor.com/sethmedlin/Family%20Travel%20Death%20Valley%20Aprilmily%20Travel%20Death%20Valley%20April%202003.htm %202003.htm

• Grand Canyon - http://www.evcforum.net/cgi-Grand Canyon - http://www.evcforum.net/cgi-bin/dm.cgi?action=msg&f=7&t=162&m=1 bin/dm.cgi?action=msg&f=7&t=162&m=1