GEOLOGY AND THE

ENVIRONMENT

The Walker School

Environmental Science

Earth’s Principal Systems

Atmosphere

Hydrosphere

Biosphere

Lithosphere

Magnetosphere

Cryosphere

Interaction Among Earth’s Systems

Table 1-1, p. 4

Earth is a Dynamic Planet

Geologic Hazards

Renewable Soil

Nonrenewable

Minerals

Energy Resources

Change is

the Norm

WHAT IS THE EARTH’S

STRUCTURE?

Earth’s Structure

The Moho, is the

boundary between the

Earth's crust and the

mantle. The Moho

serves to separate

both oceanic crust and

continental crust from

underlying mantle.

Seismic S & P Waves

Fig. 11-9b, p. 345

Seismic waves

provide evidence

that Earth’s internal

structure is layered,

not homogeneous.

Internal Processes

Convection Cells

Mantle Plumbs

(upwellings)

Plutonic Bodies

Plutonic Bodies

Fig. 4-24, p. 123

B: > 100 km2

S: <100 km2

L: inflated sills.

Internal Processes

Volcanic Bodies

External Processes

Mantle Plumbs and Interplate Hotspots

Fig. 2-22, p. 58

Mantle plumbs are

stationary, while the

plates move. This activity

has caused the creation

of new Hawaiian Islands

over the past 12 million

years.

Volcanic National Park, HIhttp://www.nps.gov/havo/

Fig. 5-3a, p. 137

Lava Tube in Hawaii

Most geographically isolated group of islands on

Earth; features include new cinder cones, glowing pit

craters, rivers of lava and fountains of spatter;

volcanic features at mass to the lithosphere, water to

the hydrosphere, carbon dioxide to the atmosphere,

and nutrients for plants.

WHAT IS PLATE

TECTONICS?

Earth’s crust is about 5% of it’s mass.

Earth has 15 Major Plates

Fig. 1-11, p. 17

Environmental Role of Plate Movement

Changes Climate

Stimulates Evolution

Changes Migratory

Patterns

Scope of the last Ice Age, 1200 BCE

Mantle (lithosphere)

Mantle (asthenosphere)

Ab

ys

sa

l p

lain

Mantle(lithosphere)

Oceanic crust

(lithosphere)

Abyssal

hills Abyssal

floor

Oceanic

ridge

Trench

Volcanoes

Folded mountain belt

Craton

Continental crust(lithosphere)

Continentalrise

Continentalslope

Continentalshelf

Abyssal plain

Abyssal

floor

Major Features of the Earth’s Crust

Convection from the Earth’s mantle rises and cools, driving the movement of the plates,

which in turn causes the folding of the lithosphere creating mountains and volcanoes.

Connections, Plates and Earth Systems

Table 1-3, p. 18

Convergent Plates

Fig. 2-18c, p. 53

Primarily responsible

for mountain building

events.

Continental Crust

Composed of many rock

types.

Can be as old as 4

billion years.

Varies in thickness from

20 to 80 km.

Makes up about 41% of

Earth’s surface.

Grand Teton National Park, WYhttp://www.nps.gov/grte

The Grand Tetons are one of the younger

mountain ranges on Earth. 24% of the Earth's

land mass is mountainous. 10% of people live

in mountainous regions. Most of the world's

rivers are fed from mountain sources, and

more than half of humanity depends on

mountains for water.A mountain is usually produced by the

movement of lithospheric plates,

called orogenic movement.

Mountain

Ice and snow

Altitude

Tundra (herbs,

lichens,

mosses)

Coniferous

Forest

Tropical

Forest

Deciduous

Forest

Tropical

Forest

Deciduous

Forest

Coniferous

Forest

Tundra (herbs,

lichens, mosses)

Polar ice

and snow

Latitude

Alpine Climate Zones

Divergent Plates

Builds new crust.

Atlanta Ocean is

getting bigger,

while the Pacific is

decreasing in size.

Mid-Atlantic Ridge & Iceland

One of the few places on earth that a

divergent pate is evident on land.

Divergent Plates Rift to Form Oceans

Fig. 2-15, p. 48

Rifting between the African

and Arabian Plate formed

the Red Sea.

Stages of Ocean

Basin Formation

Oceanic Crust

5 to 8 km thick.

Composed mainly of basalt and

gabbro.

Not older than 180 million

years.

Covered with dead organism

and sediment, about 1 km thick.

Little variability in composition.

Dunes Lagoon

SpitsStream

Glacier

Lake

Tidalflat

Barrierislands

Shallow marineenvironment

Volcanicisland

Coral reef

Abyssal plain

Deep-sea fan

Continental shelf

Continental slope

Continental rise

DeltaDunes

Beach

Shallow marineenvironment

Costal Features

WHAT GEOLOGIC PROCESSES

OCCUR ON THE EARTH’S SURFACE?

Weathering vs. Erosion

Weathering the decomposition of earth rocks, soils

and their minerals through direct contact with the

planet's atmosphere. Weathering occurs in situ, or

"with no movement", and thus should not to be

confused with erosion, which involves the movement

and disintegration of rocks and minerals by agents

such as water, ice, wind, and gravity.

Formation of the Grand Canyonhttp://www.youtube.com/watch?v=ktf73HNZZGY

Debris flows shown

in this clip erode

rock along the walls

of the canyon.

Arches National Parkhttp://www.nps.gov/arch/National

Fig. 6-CO, pp. 168-169

Erosion takes place

at different rates –

called differential

erosion

Produces: hoodoos,

spires, arches, and

pedestals

Hoodoos, Bryson Canyon National Parkhttp://www.nps.gov/brca/

Types of Weathering

Mechanical

Chemical

Biological

Fig. 6-1a, p. 170

Weathering of Granite

Physical Weathering

Mechanical or physical

weathering involves the

breakdown of rocks and

soils through direct

contact with atmospheric

conditions such as heat,

water, ice and pressure.

Badlands, SD

Chemical Weathering

Chemical weathering,

involves the direct effect

of atmospheric

chemicals, or

biologically produced

chemicals (also known as

biological weathering),

in the breakdown of

rocks, soils and minerals.

Lichens are part fungi

and part algae. They

derive their nutrients

from the rock and

contribute to chemical

weathering.

Biological Weathering from Plants

Fig. 6-6b, p. 174

Trees and other plants in

Lassen Volcanic National Park,

CA help break down parent

material into smaller pieces

and contribute to mechanical

weathering.

Salt Weathering (haloclasty)

Mechanical

Derives from an external source

(capillary rising ground water,

eolian origin, sea water along

rocky coasts, atmospheric pollution).

Favored by dry conditions in arid

climates.

The expanding salt crystals exert a

pressure on the walls of the rock

pores that exceeds the tensile

strength of the rock.

Marine Abrasion of Granite.

Isotasic Rebound

from Glaciers

Fig. 11-17, p. 351

Grosser Aletschgletscher, Switzerland

WHY DO EARTHQUAKES

OCCUR?

Earthquakes

Most occur along subduction zones and strike-slip

zones

Some occur in aseismic zones

Movement of magma causes tremors

Elastic Rebound Theory

Proposed by Henry F Reid in 1910

Rocks along a fault move relative to each other and

can bend elastically

Energy released from the bending causes shock

waves, which emanate from the plane of rupture

Liquefaction ofrecent sedimentscauses buildingsof sink

Landslides mayoccur onhilly ground

Shockwaves

Epicenter

Focus

Two adjoining platesmove laterally alongthe fault line

Earth movementscause flooding inlow-lying areas

HOW ARE EARTHQUAKES

MEASURED?

Measurements

Intensity

Amplitude

Duration

Scales

Richter Scale

Measurement of energy released for smaller and approximate earthquakes

Surface Wave Magnitude Scale

Measurement of energy released for extremely large earthquakes at a distance

Moment Magnitude Scale

Estimates the amount of displacement and area of rupture along the fault

Mercalli Scale

Directly describes the intensity of shaking rather than the magnitude

Useful in comparing damage from earthquakes at different locations

Seismographic Reading

Seismic Wave and Their Destructive Patterns.

Primary Modes of Destruction

Consolidation

Liquefaction

Vibration

Earthquake damage in a Afghan village.

Secondary Effects of Earthquakes

Rockslides

Urban Fires

Flooding

Tsunamis

Building Damage

Loss of Life

Canada

United States

No damage expected

Minimal damage

Moderate damage

Severe damage

Expected Damage From

Earthquakes

Global Seismograph Networkhttp://www.iris.edu/about/GSN/

Indian Ocean Earthquakehttp://en.wikipedia.org/wiki/2004_tsunami

Tsunamis

A series of waves created when a body of water, such as an ocean, is rapidly displaced.

Earthquakes, mass movements above or below water, some volcanic eruptions and other underwater explosions, landslides, underwater earthquakes, large asteroid impacts and testing with nuclear weapons at sea all have the potential to generate a tsunami.

As the tsunami approaches the coast and the waters become shallow, the wave is compressed due to wave shoaling and its forward travel slows and its amplitude grows enormously, producing a distinctly visible wave.

Tsunami Warning System

WHAT ARE VOLCANOES?

Distribution of Volcanoes

Circum-Pacific

Belt (60%)

Mediterranean

Belt (20%)

Mid-Oceanic

Ridges (20%)

Fig. 5-20, p. 151

More common along both divergent than convergent plate boundaries.

Mainly composed of intrusive magma flows.

Composed of mafic magma that forms beneath spreading plates.

Pyroclastic materials are not common because lava is fluid.

Water pressure prevents gasses from expanding and escaping.

extinctvolcanoes

magmareservoir

centralvent

magmaconduit

Solidlithosphere

Upwellingmagma Partially molten

asthenosphere

General Structure

Crater Lake, OR Caldera

Caldera Floor of Crater Lake

Wizard Island, Crater Lake, OR

Learn About Megavolcanos Around the Worldhttp://www.pbs.org/wgbh/nova/megavolcano/about.html

VOLCANIC MONITORING

Important Monitoring Techniques

Fig. 5-23, p. 159

Fumarole Gas Monitoring

Chemically-selective sensors for SO2 and CO2 measure gas concentrations and a wind sensor measures wind speed and direction.

Data from solar-powered stations are transmitted to GOES geostationary satellite and then down to observatories every 10 minutes, providing near real time data on degassing of volcanoes

Ground Deformation Monitoring

Paint

Electronic Distance Meters

determine the horizontal movements that occur on active volcanoes

Tiltmeters

leveling surveys to measure vertical motions

Global Positioning Systems

allows us to measure horizontal motions much more accurately and conveniently, and also to estimate vertical motions in the same survey

Remote Sensing

The Advanced Very High Resolution Radiometer (AVHRR) is a space-borne sensor embarked on the NOAA family of polar orbiting platforms.

The primary purpose of these instruments is to monitor clouds and to measure the thermal emission (cooling) of the Earth.

The main difficulty associated with these investigations is to properly deal with the many limitations of these instruments, especially in the early period (sensor calibration, orbital drift, limited spectral and directional sampling, etc).

Primary Effects of Volcanoes

Pyroclastic Flows

Fumaroles

Landslides

Ash Fall

Earthquakes

High Temperatures

Secondary Effects of Explosions

Suffocation from Ash

Asphyxiation from

Volcanic Gasses

Tsunamis

Temperatures Decreases

Ash can coat your lungs, causing the

formation of a quick cement,

asphyxiating you.

Environmental Effects

Involved in the formation of continental crust and offset weathering and erosion

Provide nutrient rich soils

By trapping clouds at their peaks, water for agriculture

Agriculture based cultures are attracted to their bases

Volcanic soils in Sumatra.

Volcanic Gasses

Water Vapor

Carbon Dioxide

Nitrogen

Sulfur Dioxide

Hydrogen Sulfide

Carbon Monoxide

Hydrogen

Chlorine

Fig. 5-2, p. 136

Gasses emitted from fumaroles at the Sulfur Works in Lassen

Volcanic National Park, CA

Effects of Volcanoes on Climate

Nucleation, condensation, and sedimentation of aerosols (acid rain)

Change in Albedo from ash cloud

Tropospheric cooling from the addition of sulfur to the stratsophere

Ozone destruction through the formation of atomic chlorine

HYDROTHERMAL VENT

ECOLOGY

Hydrothermal Vents

Distributes heat and drives water circulation in the ocean through convection

Provides energy source in the form of hydrogen sulfide to benthic chemotrophs

Distributes minerals and influences the composition of the ocean

Hydrothermal Vent Ecosystem The chemosynthetic bacteria

grow into a thick mat which

attracts other organisms

such as amphipods and

copepods which graze upon

the bacteria directly. Larger

organisms such as snails,

shrimp, crabs, tube worms,

fish, and octopuses form a

food chain of predator and

prey relationships above

the primary consumers. The

main families of organisms

found around seafloor vents

are annelids,

pogonophorans,

gastropods, and

crustaceans, with large

bivalves, vestimentiferan

worms, and "eyeless" shrimp

making up the bulk of non-

microbial organisms.

Location of Major Vent Systems

Hydrothermal Vent Chemistry

Learn More About Ventshttp://www.divediscover.whoi.edu/vents/index.html