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M&R Geography-Geology
The Physical Earth













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On this page, we will look at the physical earth -- the structure and processes that shape our planet. 
 
The earth is part of the solar system -- the 3rd planet from the sun.

Earth Statistics and Views of the Earth from Space

The earth is a dynamic planet -- constantly changing in both violent and subtle ways.
 
Geologists have measured the age of the earth at 4.6 billion years from the time it became solid -- possibly as old as 10 billion going back to its formative stages.
 
The surface consists of continents and oceans -- around 30% land, 70% water.
 
It is of course the land where people live -- and it it from this perspective that a knowledge of the land surface and what it means to people becomes important.
 
First, a look at the general structure of the earth:
 
 
 

Earth Structure

Test your knowledge of continents and oceans

Foucault Pendulum and Earth Rotation

Motion of material inside the earth produce dramatic changes on the surface.  These include volcanism and movements of the solid crust (diastrophism).
 
The events produce positive relief forms of the continents and other masses of land.

Fundamentals of Physical Geography

Minerals and Rock

Minerals and Rocks Slide Show

Types of Volcanoes

Diastrophism -- Movements in the solid crust of the Earth

These Internal Forces produce features on the land surface called 'Landforms' -- the branch of Geology that studies this subject is called Geomorphology.
 
For many years the forces behind this restlessness of the crust were not known.  Today, the Theory of Continental Drift and its complementary Theory of Seafloor Spreading give us the answers.
 
Together these theories are called Plate Tectonics.
 
 

Plate Tectonics Discussion

Another set of forces act to modify the surface produced.
 
These are the External Forces -- Weathering and Erosion.
 
Weathering is a complex of processes that disintegrate rock into smaller pieces or new materials.  Weathering is two general processes called Physical Weathering -- reducing rock particle size; and, Chemical Weathering which changes the rock's compostion into simpler (chemically) earth materials.
 
 

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Physical Geography Resources

World Elevation Zones

The Water Cycle

Weathering of Rock

Photos and Discussion of Rock Formations

Through the action of the plates, colliding, pulling apart, or sliding past each other the major landforms of the earth are produced.
 
The major landforms are Mountains, Hills, Plateaus, and Plains -- and it is upon these surfaces that people must live.  Each has it advantages and disadvantages.
 
Mountains  --  Bring ancient rock to the surface in many cases, where
                    metal ore minerals may be found.
 
                    Due to the orographic effect, mountains are often  
                    forested.
 
                    Beautiful scenery provides recreational opportunities.
 
                    Rivers and canyons provide sites for hydroelectric
                    dams.
 
Hills  --          Hills may be as steep as mountains, but the slopes are 
                    not as long.
 
                    Hills may have many of the geographic resources as
                    mountains.
 
Plateaus --     Plateaus are relatively level surfaces high above sea 
                    level.
 
                    Oftentimes somewhat drier than surrounding areas
                    land use is limited to livestock production and dry
                    farming.
 
                    Deep canyons cut through plateaus disrupt 
                    transportation, but do afford places for dams and
                    hydroelectric development.
 
Plains  --       Plains are relatively level areas close to sea level.
 
                   Advantages often include fertile soil for farming, ease of
                   transportation, and availability of fuels -- coal, oil, and
                   natural gas. 
 
                               Most of the world's people live in areas of plains.

Forces of erosion immediately begin to affect any newly produced landform -- all landforms are constantly in the process of being built on the one hand and being destroyed on the other.  At any time and place one of the forces -- constructive or destructive -- may be the dominant factor.
 
The major forces of erosion are Running Water, Wind, and Glacial Ice.
 
As the forces of erosion attack the rock structure, various relief forms are produced according to the pattern of rock being weathered and eroded.

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Cycle of Erosion (Running Water)

Online Earth Science Tutorials

Tutorial -- Landforms produced by running water

Tutorial -- Landforms produced by volcanoes

Tutorial -- Landforms produced by diastrophism

Tutorial -- Landforms produced by wind

Tutorial -- Landforms produced by glaciers

Tutorial -- Coastal landforms

Tutorial -- Landforms produced by groundwater

Tutorial -- Landforms produced by Mass Wasting

Weather & Climate