Earth Processes Educational Posters & Charts for Geology
for the science and social studies educator and home schoolers.

Earthquakes

When the plates of the Earth's crust move and collide with each other the forces create vibrations. These vibrations are commonly known as earthquakes. Earthquakes occur around the globe almost non-stop. Some are barely detectable and others create such destructive vibrations that whole cities can be shaken down to little more than rubble. Although volcanic eruptions and atomic explosions can cause earthquakes, most occur along plate boundaries where techonic forces build up.

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Earth's Structures

Our planet Earth is composed of different spheres (or layers) of rock, solid, or liquid. The upper mantle, however, has both molten rock and solid rock moving around in currents risings and falling in a boiling motion, this area of the mantle is known as the asthenosphere. It is upon this layer that the crust of the Earth floats and moves as separate plates, colliding into one another and sliding over and under each other as well. this concept of plate movement is the basis of plate tectonics. Although it feels as if we are living on a solid world, it is in fact ever moving and ever changing.

Erosion & Weathering

Wind, rain and other forces are constantly shaping and rearranging the Earth's surface. This process of change is known as erosion and weathering. Erosion is the process of removal and transportation of Earth's materials by natural forces. These forces can include rain, wind, rivers, glaciers, earthquakes, and volcanoes.

Weathering is similar to erosion except it does not include the transportation of materials. It is the process of rock breakup resulting from exposure to the atmosphere. Mechanical weathering involves the physical breakup of rock, without altering the chemical makeup of the minerals compounding it. An example of mechanical weathering is when ice expands to break apart rock. If the chemical makeup is altered, it is referred to as chemical weathering. Rust is a form of chemical weathering.

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Faults & Folds

Forces created by plate tectonics act upon the rock that composes the plates, causing them to fold (bend) or fault (break) at their boundaries. These tectonic forces are responsible for the building of mountains.

There are three types of plate boundaries. Plates can move along side each other, this is known as a transform boundary, where asthenosphere are found. Plates can move toward one another, causing one plate to slide under the other plate, this is referred to as an convergent boundary, which produces reverse faults. The divergent boundary, where plates move away from each other, leaves a space where magma from the asthersophere seeps up and cools to form new crust; a normal fault is developed at ths type of boundary.

There are two types of folds: an anticline, which is the plate folding upwards in the shape of a mountain, or a syncline, in which the plate folds downward in the shape of a valley.

Glaciers

In the regions closest to the poles, or regions so high in elevation that snowfall accumulation exceeds the amount that melts off over long periods of time, glaciers can be formed. As the snow compacts into ice, the weight causes it to begin moving down a mountain, carving huge valleys and sculpting mountains. Motion and change are what glaciers are all about. Glaciers have been responsible for shaping most of the Earth's surface, either by direct carving from the ice flow or from the water runoff caused by glacial melting. As the glacier carves and breaks down rock, it can relocate massive amounts of rock over large areas. Glaciers typicaly move slowly, but great land transformations over a short geological time period (such as 100 years) have been recorded.

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Plate Tectonics / Plate Boundaries and Movement

The theory of plate tectonics describes the Earth's crust (the lithosphere) as segmented into several plates, which float and move on a soft layer (the asthenosphere) consisting of solid and molten rock. The asthenosphere currents, created by the heat deep inside the Earth, move and push the plates across the Earth's surface. These plates are in constant motion – colliding, separating and rubbing against each other, creating volcanoes, earthquakes and many other geological events. The theory of plate tectonics is relatively new, and is associated with technological advances and discoveries in the 1950s and 60s. It builds upon earlier theories including continental drift and sea-floor spreading.
Plate Boundaries and Movement

Volcanoes

Deep inside the Earth, heat and pressure cause solid rock to melt into a liquid known as magma. In some areas around the globe this magma has risen to the surface and erupted, creating volcanoes. Volcanoes are generaly classified into three types: Shield Volcanoes, Composite Cone Volcanoes and Cinder Cones.

Shield volcanoes are broad, domed mountains formed from highly liquid magma flowing and cooling slowly to form rock. As one eruption cools another eruption flows over it, building layers of cooled lava flows. These volcanoes erupt primarily liquid magma, or lava, as it is called once it reaches the Earth's surface.

Composite cone volcanoes are more explosive in nature. The lava fragments are cooled in the air, forming pyroclastic material. The next eruption might be more liquid, thus it has alternating layers of pyroclastic material and lava flows. This type of volcano has much steeper sides.

Cinder cones are primarily built up with pyroclastic material around a central vent. This is common in larger volcanoes.

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