14-1 What Are the Earth’s Major

Geological Processes and Hazards?• Concept 14-1A Gigantic plates in the

earth’s crust move very slowly atop the

planet’s mantle, and wind and water move

the matter from place to place across the

earth’s surface.

• Concept 14-1B Natural geological

hazards such as earthquakes, tsunamis,

volcanoes, and landslides can cause

considerable damage.

• 3rd Planet from sun

• Formed ~4.6 billion years ago

• Shape = oblate sphere

Caused by Earth’s rotation

• Difference between tallest

mountain and deepest ocean

trench is ~20 km

40,007 km around

40,074 km around

3 major concentric zones of earth’s interior

Crust (Continental and Oceanic-71%)

Mantle

Core

Structural zones of earth’s interior

Lithosphere

Asthenosphere

Mesosphere

Outer Core

Inner core

Earth’s Interior

Major Features of the Earth’s

Crust and Upper Mantle

Plate Tectonics

Alfred Wegener’s

Hypothesis

Continental Drift: Hypothesis that the

continents once formed part of a single

landmass called a supercontinent

Began breaking up ~250 million years ago

Continents drifted to present location

Evidence of Continental Drift

Fossil Evidence

Fossils found of same species in areas where

continents were once connected

Evidence from Rock Formations

Ages and types of coastal region rocks matched

closely

Climatic Evidence

Glacier deposits where climates are warm

Mid-Ocean RidgesMid-Atlantic Ridge mapped out in 1947

Mid-ocean ridges: undersea mountain ranges through the center of which run steep, narrow valleys.

Ridge Facts

The sediment covering the sea floor is thinner closer to a ridge

Younger sediment closer to a ridge

Rocks on land ~3.8 billion years

Rocks on sea floor < 175 million years old

Magma

Oceanic

Crust

Sea-Floor SpreadingHess proposed a rift (crack at

center of ridge) that magma

flowed from, ocean floor

spreads, magma cools

forming rock and replacing

gap in ocean floor

Dietz defined this process

Sea-floor Spreading

PaleomagnetismStudy of the magnetic properties of rocks

Magnetic ReversalsNormal Polarity= rocks magnetic field points north

(classified together in same time period)

Reverse Polarity= rocks magnetic field points south

(classified together in same time period)

Magnetic SymmetryStripped magnetic pattern same on each side of the ridge

Magnetic patterns help date ocean floor and support sea-

floor spreading

Plate tectonics is the

theory that explains

why and how

continents move and

is the study of the

formation of features

in Earth’s crust

How Continents Move Lithosphere is divided into tectonic plates, which can also include continental crust, oceanic crust, or both

Asthenosphere is under great pressure, therefore flows (moves) slowly allowing the tectonic plates to move above it

Tectonic PlatesAbout 7-8 Major Plates (+7-8 more

minor plates)

Primarily identified using earthquake

data

Frequent earthquakes is evidence of a

boundary

Volcanoes are also an identifier when

they form from magma generated

during plate motion

The Earth’s Major Tectonic Plates

Types of Plate Boundaries

The San

Andreas Fault

as It Crosses

Part of the

Carrizo Plain

in California,

U.S.

Causes of Plate Motion

Mantle Convection

Ridge PushThe asthenosphere exerting force on the plate

pushing the plate away from the ridge

Slab PullThe force exerted

by the sinking plate

Direction of plate motion

Sinking due to densityResulting plate motion

Resulting plate motion

Sinking lithosphere

Moving asthenosphere

Rifting and Continental ReductionRifting: the process by which a

continent breaks apart

Rifts form because heat builds up

under the insulating continent, the

lithosphere becomes thinner (weaker),

the continent breaks apart at the

weakness

Terranes and Continental Growth

Terrane: A piece of lithosphere that has

a unique geologic history that differs from

the histories of the surrounding lithosphere

3 Characteristics:

1.Rocks and Fossils differ between terranes

2.Major faults at terrane boundaries

3.Magnetic properties differ between terranes

AccretionThe process in which a terrane becomes part of a continent

Occurs at Convergent Boundaries

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Effects of Continental Change

Changes in ClimateLarge continent mass was located near the South

Pole so was covered by ice

When continents moved toward equator the ice

melted

Changes in LifeRifts and Mountains separate species

Species evolve differently when separated and

new species may emerge

Supercontinent Cycle

Some Parts of the Earth’s Surface

Build Up and Some Wear Down

Internal geologic processes

- Generally build up the earth’s surface

External geologic processes

– Weathering• Physical, Chemical, and Biological

– Erosion• Wind

• Flowing water

• Human activities

• Glaciers

Weathering: Biological,

Chemical, and Physical

*SEE WEATHERING

AND EROSION

POWERPOINT!

Volcanoes Release Molten Rock

from the Earth’s Interior

• Volcano

– Fissure: Central vent or long crack

– Magma: Partially molten asthenosphere

– Lava: Magma that reaches the earth’s

surface

• Benefits of volcanic activity

– Scenery

– Fertile soil produced by weathering of lava

May 18, 1980 Eruption of

Mount St. Helens• Elevation of summit: 9,677 feet

before; 8,363 feet after;

• Magnitude 5.1 earthquake at 8:32 a.m.

• Fatalities

– Human: 57

– Wildlife: Countless non-burrowing wildlife in blast

area, including about 7,000 big game animals;

about 12 million salmon fingerlings in hatcheries

1991 Eruption

of Mount

Pinatubo,

Philippines

• Eruption was Forecasted!

– Resulted in the saving of at least 5,000 lives

and at least $250 million in property

– However, a few jets flying far to the west of the

Philippines encountered ash and sustained

about $100 million in damage

Creation of a Volcano

Earthquakes Are Geological

Rock-and-Roll Events• Earthquake

– Seismic waves: form of energy vibrations

– Focus: location where earthquake begins BELOW the surface

– Epicenter: location ABOVE the surface over focus

– Magnitude: measure of ground motion

– Amplitude: size of the seismic wave

Richter Scale• Developed in 1935 by Charles F. Richter

– California Institute of Technology

– Magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs.

• Richter scale – Insignificant: <4.0

– Minor: 4.0–4.9

– Damaging: 5.0–5.9

– Destructive: 6.0–6.9

– Major: 7.0–7.9

– Great: >8.0

Earthquakes Are Geological

Rock-and-Roll Events• Foreshocks: occurs from seconds to

weeks BEFORE the main shock

• Aftershocks: occurs months after main

shock, but will decrease in frequency

over time

Major Features and Effects of

an Earthquake

Areas of Greatest Earthquake Risk in

the United States

Areas of Greatest Earthquake Risk

in the World

1995, Kobe (Japan)

• The 1995 Great Hanshin

Earthquake (M=6.9), commonly

referred to as the Kobe

earthquake, was one of the

most devastating earthquakes

ever to hit Japan.

• More than 5,500 were killed

and over 26,000 injured.

• The economic loss has been

estimated at about $US 200

billion.

The San Francisco earthquake in 1989 killed nine

people and injured hundreds.

The earthquake was measured to be a 6.9

Which caused collapsed bridges and freeways,

fires, shattered buildings, gaping cracks in roads

and land slides

San Francisco earthquake

1989 earthquake in san Francisco caused a lot

of damage to the city

Earthquakes on the Ocean Floor Can

Cause Huge Waves Called Tsunamis

• Tsunami (tidal wave): series of large waves

generated when ocean floor suddenly rises or drops

• Detection of tsunamis: ocean buoys, pressure

recorder (data relayed to weather buoy)

December 2004: Indian Ocean tsunami

• Magnitude of 9.15

• Waves height: 31 meters (100 feet)

• 228,000 people died

• Role of coral reefs and mangrove forests

in reducing death toll

– Sri Lanka-illegal coral mining and reef

damage were factors in causing the greatest

damage here

Formation of a Tsunami and Map of

Affected Area of Dec 2004 Tsunami

Shore near Gleebruk in Indonesia

before and after the Tsunami on

June 23, 2004

Gravity and Earthquakes Can

Cause Landslides• Mass wasting

– Slow movement

– Fast movement

• Rockslides

• Avalanches

• Mudslides

• Effect of human activities on such

geological events

– Forest clearing, road building, crop growing

California PCH and Malibu

How Are the Earth’s Rocks Recycled?

• Concept 14-2 The three major types of

rocks found in the earth’s crust—

sedimentary, igneous, and metamorphic—

are recycled very slowly by the process of

erosion, melting, and metamorphism.

Three Major Types of Rocks

Earth’s crust

• Composed of minerals and rocks

Three broad classes of rocks, based on

formation

1. Sedimentary formed by the lithification of weathered

rock debris that has been physically transported and

deposited

• Sandstone

• Shale

• Dolomite

• Limestone

• Lignite

Three Major Types of Rocks

2. Igneous: formed by the cooling and

solidification of molten magma

• Granite

• Lava rock

3. Metamorphic: alteration of existing rocks by either excessive heat and pressure, or through the chemical action of fluids.• Anthracite

• Slate

• Marble

Natural Capital: The Rock Cycle Is the

Slowest of the Earth’s Cyclic Processes

4 Characteristics of Minerals

1. It is INORGANIC

2. It OCCURS NATURALLY

3. It is a CRYSTALLINE SOLID

4. It has CONSISTENT CHEMICAL

COMPOSTION

Silicate Minerals

Minerals that contain a combination

of silicon and oxygen

Make up 96% of Earth’s crust

Feldspars are the most common

silicates

Silicate Minerals

Chemical CompositionKalSi308 – Potassium

Aluminum Silicate

Color

Typically off-white or

shades of red, orange

and brown, occasionally

green.

Cleavage

One perfect cleavage

and one good cleavage

that meet at nearly 90°

Hardness 6 (harder than glass)

Specific Gravity 2.6

Luster

Crystals are vitreous

(glass-like) to

porcelaneous (porcelain-

like)

Streak white

Potassium Feldspar

Nonsilicate Minerals

Do not contain silicone-oxygen

compounds

~ 4% of Earth’s Crust

1. Carbonates

2. Halides

3. Native elements

4. Oxides

5. Sulfates

6. Sulfides

Nonsilicate Minerals

PyriteAKA

“Fools Gold”

Crystalline Structure of silicates

Crystalline Structure of nonsilicates

Examples include cubes,

hexagonal prisms, and

irregular masses

Identifying using Physical

Properties

• Color

• Streak

• Luster

• Cleavage and

Fracture

• Hardness

• Crystal Shape

• Density

There Are Several Ways to

Remove Mineral Deposits• Surface mining

– Shallow deposits removed

• Subsurface mining

– Deep deposits removed

• Type of surface mining used depends on

– Resource

– Local topography

There Are Several Ways to

Remove Mineral DepositsTypes of surface mining

– Open-pit mining: digging holes to remove ores

(e.g. iron, copper, gold) and sand, gravel, or stone

– Strip mining: extract minerals on surface in

large horizontal beds

– Contour mining: cutting terraces into side of

hill or mountain

– Mountaintop removal: remove entire top of

mountain

Natural Capital Degradation: Open-

Pit Mine in Western Australia

Natural Capital Degradation: Contour Strip

Mining Used in Hilly or Mountainous Region

Natural Capital Degradation: Mountaintop

Coal Mining in West Virginia, U.S.

Mining Has Harmful

Environmental Effects• Scarring and disruption of the land surface

– E.g., spoils banks (a series of hills left behind

from area strip mining)

• Loss of rivers and streams

• Subsidence: the collapse of land above

some underground mines

Mining Has Harmful Environmental Effects

• Major pollution of water and air

– Acid mine drainage: rainwater seeps through

mine and carries H2SO4 to groundwater

• Effect on aquatic life

– EPA says 40% of watersheds in US are

polluted

• Large amounts of solid waste

– 75% of all US solid waste

Banks of Waste or Spoils Created by Coal

Area Strip Mining in Colorado, U.S.

Illegal Gold Mine

Ecological Restoration of a Mining

Site in New Jersey, U.S.