Physical Science

Geography 1000 Earth's Surface and Environments 

Tracking Earthquakes and Volcanoes

Part One: Tracking Earthquakes

Earthquakes are the Earth's natural means of releasing stress. When the Earth's plates move against each other, stress is put on the lithosphere. When this stress is great enough, the lithosphere breaks or shifts. When the break occurs, the stress is released as energy which moves through the Earth in the form of waves, which we feel and call an earthquake. This portion of my ePortfolio tracks earthquakes along different plate boundaries. Below I have listed four earthquakes of magnitude 4.0 or greater at each plate boundary.

1. Oceanic-Oceanic

An Oceanic-oceanic convergence is when two oceanic plates converge and one is usually subducted under the other and in the process a deep oceanic trench is formed. Below is a current location of an earthquake in the Aleution Islands.

2. Oceanic-Continental

Oceanic-Continental Convergence is when an oceanic plate pushes into and subducts under a continental plate. Such earthquakes are often accompanied by uplift of the land by as much as a few meters. The following screenshot illustrates a current earthquake off the coast Oregon.

3. Continental-Continental

Continental-Continental is when two plates converge, buckle, fold and fault to form complex mountain ranges of great height.

4. Divergent

A divergent boundary is a linear feature that exists between two tectonic plates that are moving away from each other. These areas can form on the end of continents and eventually form ocean basins, resulting in new crust being added to the surface of the earth. Divergent boundaries can also develop within a continent, resulting in a continental rift valley which is the process of the spreading of the earth’s surface. Below is an illustration of an earthquake that took place at the edge of a continent.

5. Transform

Transform-Fault Boundaries are where two plates are sliding horizontally past one another; commonly know as faults. Most transform faults are found on the ocean floor. A few, however, occur on land. Below is an image of a current earthquake.

Part Two: Identifying Volcanoes

A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface. Volcanoes are generally found where tectonic plates are diverging or converging. This portion of my eportfolio focuses on the four different types of volcanoes.

1. Oceanic-Oceanic

Oceanic volcanoes are aligned along the crest of a broad ridge that symbols an active fracture system in the oceanic crust. Volcanic rock generated in the upper mantle beneath the ridge, rise along cracks through the basaltic layer.

2. Oceanic-Continental

Oceanic-Continental volcanoes are located in unstable, mountainous regions that have thick roots of granite like rock. Magmas generated near the base of the mountain, rise slowly along fractures in the crust. During course through the granite layer, magmas are commonly changed in composition and erupt on the surface to form volcanoes constructed of non-basaltic rocks.

3. Divergent

Divergent boundaries also form volcanic islands which occur when the plates move apart to produce gaps which molten lava rises to fill. Thus creating a shield volcano which would eventually build up to become a volcanic island. two plates move apart from each other and the space that this creates is filled with new crustal material sourced from molten magma that forms below.

4. Hotspots

Hotspots are thought to be caused by a narrow stream of hot mantel convecting from the Earth's core-mantel boundary called a mantel plume. Most hotspot volcanoes are basaltic because they erupt through oceanic lithosphere.