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:
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.
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
Beautiful scenery provides recreational opportunities.
Rivers and canyons provide sites for hydroelectric
Hills -- Hills may be as
steep as mountains, but the slopes are
not as long.
Hills may have many of the geographic resources as
Plateaus -- Plateaus are relatively level surfaces high above
Oftentimes somewhat drier than surrounding areas
land use is limited to livestock production and dry
Deep canyons cut through plateaus disrupt
but do afford places for dams and
Plains -- Plains are relatively level areas
close to sea level.
often include fertile soil for farming, ease of
transportation, and availability of fuels -- coal, oil, and
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.
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