PS 100 -- Chapter 31 1

31 The Changing Face of the Earth

Flooding of Mississippi & Illinois Rivers 1993

Before After

PS 100 -- Chapter 31 2

At which type of plate boundary would you expect to find large, deep focus earthquakes, but no volcanoes?

1 2 3 4

25% 25%25%25%1. Continent-continent collision boundary

2. Continental rift boundary

3. Transform boundary

4. Ocean-ocean collision boundary

PS 100 -- Chapter 31 3

What is a Natural System?

Group of natural, interdependent parts or components

Interactions between parts forms the system Forces drive the system All systems tend toward a state of maximum

disorder (entropy) called equilibrium Earth’s two major systems are:

Hydrologic System Tectonic System

PS 100 -- Chapter 31 4

Hydrologic System System of moving

water Rivers Oceans, Lakes Glaciers Groundwater Water Vapor in

Atmosphere

Effects of Hydrologic System Erosion Transportation of

Sediment Deposition of

Sediment Creation of Numerous

Landforms

PS 100 -- Chapter 31 5

Hydrologic System

PS 100 -- Chapter 31 6

Where is Water Found in the Hydrologic System?

Ocean

Glaciers

All Other

97%

2.2

0.7

0.013

0.0045

0.0009

0.0184

Glaciers

Groundwater

Lakes &Rivers

Soil

Atmosphere

PS 100 -- Chapter 31 7

What Forces Drive this System? Solar Radiation

Average ~342 W/m2 = ~342 joules/sec m2

Causes evaporation

GravityPulls water down slopesCausing erosion, transportation of sediment

PS 100 -- Chapter 31 8

Subsystems of Hydrologic System River Systems Glacial Systems Groundwater

Systems Ocean/Shoreline

Systems Desert Systems

PS 100 -- Chapter 31 9

Rivers Primary mechanism for

erosion Move sediment from

mountains to oceans Also carry dissolved ions

(salts) Can be easily disturbed

by human activity Dams Pollution Irrigation

PS 100 -- Chapter 31 10

PS 100 -- Chapter 31 11

PS 100 -- Chapter 31 12

Glaciers Rivers of Ice Very effective agents of erosion Carve different topography than rivers Many glaciers are currently shrinking due to global

warming

PS 100 -- Chapter 31 13

PS 100 -- Chapter 31 14

Pasterze Glacier, Austria

1875

2004

PS 100 -- Chapter 31 15

PS 100 -- Chapter 31 16

Groundwater Rocks can hold a lot of

water! Porosity Permeability

Groundwater is a major source of drinking and irrigation water

Groundwater is often affected by human activity Overpumping Pollution Irrigation

PS 100 -- Chapter 31 17

Water Table

PS 100 -- Chapter 31 18

PS 100 -- Chapter 31 19

PS 100 -- Chapter 31 20

PS 100 -- Chapter 31 21

Oceans & Shorelines

Beautiful, but changeable

Shorelines are places of active… Erosion Transportation Deposition

Human activity can have a significant effect on shorelines

PS 100 -- Chapter 31 22

PS 100 -- Chapter 31 23 NASA

PS 100 -- Chapter 31 24 Smiley Pool, Dallas Morning News

PS 100 -- Chapter 31 25

PS 100 -- Chapter 31 26

17 July 2001

31 Aug 2005: After Katrina

17 Sep 2004: After Ivan

Dauphin Barrier Island: Alabama National Geographic

PS 100 -- Chapter 31 27

Barrier islands and wetlands

No barrier islands or wetlands: Effects of artificial subsidence & sea level rise

National Geographic

PS 100 -- Chapter 31 28

Deserts Dominated by wind

Carries light-weight particles (sand & dust)

Leaves the rest behind

Human effects Desertification

Overgrazing Poor Farming Practices

Destruction of Soil Irrigation adds salts

PS 100 -- Chapter 31 29

PS 100 -- Chapter 31 30

PS 100 -- Chapter 31 31

Climate Change All of these systems are affected by the

changing climate Earth’s climate changes naturally over time

At times in the past the Earth has been much cooler and at other times much warmer

Human activity can speed up the rate at which these changes occur Pollution

CO2 and CH4 can help hold heat around the Earth Particulates (dust and smoke) can reflect sunlight and lead to

cooling of the Earth

PS 100 -- Chapter 31 32

What is Earth’s Past History?How do we know?

PS 100 -- Chapter 31 33

PS 100 -- Chapter 31 34

What Causes Climate Change? Amount of Solar Radiation Reaching the Earth

Milankovich Cycles Distance of Earth from Sun (100,000 yr cycle) Tilt of Earth on its axis (41,000 yr cycle) Precession of Earth on its axis (23,000 yr cycle)

Amount of Solar Radiation Trapped in the Lower Atmosphere Greenhouse Effect

Carbon Dioxide Methane Water Vapor

PS 100 -- Chapter 31 35

PS 100 -- Chapter 31 36

PS 100 -- Chapter 31 37

PS 100 -- Chapter 31 38

What is the evidence that Earth is warming up?

PS 100 -- Chapter 31 39

ICE CORE DATA

PS 100 -- Chapter 31 40

Recent Sea Level Changes

PS 100 -- Chapter 31 41

Possible Human Effects on Climate

Declining CO2 trend reversed 8000 years ago Correlates with clearing of European forests & beginning of rice

cultivation Declining CH4 trend reversed 5000 years ago

Correlates with flooding of lowlands and beginning of rice cultivation

PS 100 -- Chapter 31 42

Should we do anything?

PS 100 -- Chapter 31 43

Geologic record indicates that past sea level changes when polar glaciers melt have been hundreds of meters. The cost would be catastrophic.

PS 100 -- Chapter 31 44

Risk, Cost, & Benefit Cost of reducing greenhouse emissions will

certainly be billions of dollars Certainty of global warming is not 100%

Current predictions depend on imperfect models

Environmental and economic consequences could be truly catastrophic Some say global warming could cause the end of

technological civilization

As voters & consumers, these are your issues

PS 100 -- Chapter 31 45

Climate change is caused mainly by changes in the balance between the amount of solar radiation received and the amount of heat radiated back into space by the Earth.

True False

50%50%1. True

2. False