Top Banner
CHAPTER 3 Landforms
49
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Chapter 3   Land

CHAPTER 3 Landforms

Page 2: Chapter 3   Land

Study of the landforms and the processes that create them

Geomorphology

Page 3: Chapter 3   Land

Important Points Study of the Lithosphere Elements of surface have identifiable

forms are called landforms Mountains Plains Plateaus Valleys

Landforms constantly change Geographers study topography (shape of

the earth’s surface)

Page 4: Chapter 3   Land

Processes that create landforms

Endogenic Processes Internal Forces Earthquakes Volcanoes

Exogenic Processes External

Forces Erosion Weathering

Page 5: Chapter 3   Land

Plate Tectonics

Alfred Wegener

Theorized in 1912; proven after WWII

12 large tectonic plates float on the mantle

200 million years ago, all one continent (Pangaea)

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0807/es0807page01.cfm?chapter_no=visualization

Page 6: Chapter 3   Land

Ring of Fire

Page 7: Chapter 3   Land
Page 8: Chapter 3   Land

Types of Boundaries Divergent boundaries

Spread Apart Generally mid-ocean; causes sea floor spreading Underwater volcanoes, few quakes

Convergent boundaries Push together Usually near continental edges Violent volcanoes near ocean, strong quakes

Transform boundaries Grind together No volcanoes, mild to strong quakes (San

Andreas)http://www.learner.org/interactives/dynamicearth/plate.html

Page 9: Chapter 3   Land
Page 10: Chapter 3   Land
Page 11: Chapter 3   Land
Page 12: Chapter 3   Land

Earthquakes Crust movement where

plates meet 500,000 per year; 800 felt Seismic waves of energy

(vibrations) Seismograph measures

waves Earthquakes don't kill people,

buildings (and gas mains) do Epicenter – point on the surface directly above the focus of an earthquake

Page 13: Chapter 3   Land
Page 14: Chapter 3   Land

Bam, Iran 12/26/2003

Page 15: Chapter 3   Land

San Andreas“San Francisco”

M8.5 – April 18, 1906, 3,000 deaths

$400 million in damage

Page 16: Chapter 3   Land

Rock Formation Types

Igneous – molten rock cools; basalt Sedimentary – rocks eroded from

mountains; shale Metamorphic – exposed to heat/pressure

and compressed; marble & slate Minerals (specific chemical compounds)

Sima – Dense w/silicon & magnesium; ocean floor

Sial – Less dense w/silicon & aluminum; makes up crust

Page 17: Chapter 3   Land

Stress on Rocks Fault - a break in

Earth’s crust where slabs of crust slip past each other.

They usually occur along plate boundaries where the forces of plate motion compress, pull, or shear the crust so much that the crust breaks.

Page 18: Chapter 3   Land

Normal fault The fault is at an

angle, so one block of rock lies above the fault while the other block lies below the fault.

Found near a divergent plate boundary

Page 19: Chapter 3   Land

Reverse Faults Compression

produces reverse faults.

It is like a normal fault but the blocks move in the opposite direction.

Near convergent boundaries

Page 20: Chapter 3   Land

Reverse Fault - Appalachian Mountains

Page 21: Chapter 3   Land

Strike-slip fault Strike-slip fault -

shearing causes these faults. Rocks on either side of the fault slip past each other sideways with little up-or-down motion. They also form transform boundaries.

Example - San Andreas fault

Page 22: Chapter 3   Land

Mountain Building Over millions of years,

fault movement can change a flat plain into a towering mountain range.

Mountains Formed by Faulting When normal faults uplift a block of rock, a fault-block mountain forms.

Teton Range near Wyoming and Idaho was formed this way.

Page 23: Chapter 3   Land

Mountains Formed by Folding Have you ever skidded on a rug that

wrinkled up as your feet pushed it across the floor?

Folds - bends in rock that form when compression shortens and thickens part of Earth’s crust.

Page 24: Chapter 3   Land

Mountains caused by Folding

Himalayas Alps

Page 25: Chapter 3   Land

Volcanoes Pressure on molten rock Shield volcanoes

Made of basalt More calm and constant (runny lava) Along divergent boundaries or at hot

spots Relatively less dangerous

Composite volcanoes Violent and explosive (lava & ash) About 600 active (1000s dormant) Relatively hard to predict Can cause major climate changes

Mauna Loa Shield Volcano

Page 26: Chapter 3   Land

Mt. St. Helens 5/18/1980Composite cone volcano

Page 27: Chapter 3   Land

Exogenic ForcesReshape the Earth’s crust into new landforms

Page 28: Chapter 3   Land

Weathering Process of breaking down rocks into pieces First step in the formation of soil Most mountains are going down faster than

they’re going up Mechanical weathering breaks rocks into

smaller pieces Frost action Salt crystals Roots Exfoliation

Rock chemistry does not change

Page 29: Chapter 3   Land

Frost Action

Page 30: Chapter 3   Land

Weathering Chemical weathering changes the

chemistry of rocks Oxidation (exposure to oxygen) Hydrolysis (exposure to water) Carbonation (exposure to carbon dioxide)

Warmth and water encourage chemical reactions

Weathering loosens rock particles, creates soil

Page 31: Chapter 3   Land

Oxidation

Page 32: Chapter 3   Land

Carbonation: KarstFormed by the dissolution of soluble rocksKarst regions contain aquifers that are capable of providing large supplies of water.

Page 33: Chapter 3   Land

Erosion & Deposition Erosion carries particles away Surface Erosion – water carrying particles

Rainfall Relatively slow

Running water Constant water, floods Most important landform agent in deserts Floodplains, levees, and deltas

Deposition deposits them

Page 34: Chapter 3   Land

Streams are vital geologic agents

Carry most of the water that goes from land to sea (groundwater & overland flow)

Transport billions of tons of sediment to the ocean each year

Transport billions of tons of soluble salts to the oceans each year

Shape the surface of the Earth

Page 35: Chapter 3   Land

Stream Flow

Some of the consequences of natural stream flow present engineering and social challenges with which

we grapple year after year, and have through civilization’s history.

The flow of fresh water in channels on the Earth’s surface has been essential to the development of

topography and most ecosystems.

Page 36: Chapter 3   Land

Floodplain

Delta

Levee

flat or nearly flat land adjacent to a stream or river that experiences occasional or periodic flooding

deposit at the mouth of a river is usually roughly triangular in

shape

river's banks are built up above the level of the rest of the floodplain

Meander

Page 37: Chapter 3   Land

These are satellite images before and during Summer, 1993 floods of the Mississippi river north of St.Louis.

Mississippi Floodplain

Page 38: Chapter 3   Land

Alluvial fan fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads

Page 39: Chapter 3   Land

Streams Locked in Valleys

Streams like these (and the Potomac River at Great Falls) have virtually no (normal) floodplains. They have carved into rock so deeply, that their meandering and other

characteristic evolutionary features are restricted.

Page 40: Chapter 3   Land

Glaciers

Rivers of ice Types

Alpine Glaciers – snow accumulation over years

Continental Glaciers – covers vast areas Carve out landforms from mountains Deposit material when they leave

Moraines Outwash plain

Past 200 years has seen glacial shrinking

Page 41: Chapter 3   Land

Glacial landforms

Outwash Plain- large volumes of rock and dirt debris that often spreads out in a great sheet

Terminal Moraine - accumulation of boulders, stones, or other debris carried and deposited by a glacier

Alaska

Long Island, NY

Page 42: Chapter 3   Land
Page 43: Chapter 3   Land

Glacial landforms: California

Page 44: Chapter 3   Land

Glacial landforms: Iowa

Iowa is almost entirely covered by loose sediments left behind by the continental glaciers which has created fertile soil

Page 45: Chapter 3   Land

Waves and coastlines

Waves transfer energy through wind Energy moves particles down the coast

(longshore current) Newer coastline=erosion Older coastline=deposition Tsunami – extremely long wave created

by earthquake Barrier reef: only organically formed

landformhttp://www.uky.edu/AS/Geology/howell/goodies/elearning/module14swf.swf

Page 46: Chapter 3   Land

Longshore current

Pacific Palisades

Longshore currents affect shorelines by redistributing sand and sedimentalong their path.

Page 47: Chapter 3   Land
Page 48: Chapter 3   Land

Erosion vs. deposition

Acapulco

Cancún

Page 49: Chapter 3   Land

Great Barrier Reef