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Mariana Trench is the deepest known part of the earth. This information graphic explores the wonders of Mariana Trench on both a macro-level and a micro-level. The overview of Mariana Trench, location, depth/height comparison, marine biology, and step-by-step process of its formation are featured.

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Pressure and Temperature change with Depth 

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Pressure and Temperature change with Depth 

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Earthguide: Online Classroom - Geothermal Gradients

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DK Find Out! | Fun Facts for Kids on Animals, Earth, History and more!

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Visit DK Find Out! to learn about dinosaurs, space, animals, nature & more. Fun learning activities for kids with videos, quizzes & galleries at DKFindOut.com

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The South American Plate is moving westwards due to sea floor spreading at the Mid Atlantic Ridge. Where it meets the Caribbean Plate, it descends (subducts) beneath it. This is because the oceanic lithosphere of the South American Plate is cooler and denser than that of the Caribbean Plate. The subduction causes low density ocean floor sediment to be scraped off the surface of the South American Plate and thrust onto the Caribbean Islands as accretionary wedges, in a process called obduction. The line of subduction is marked by the deep sea Puerto Rico Trench.

As the South American Plate descends, it drags against the overlying plate, causing both to fracture and deform. This results in frequent shallow focus earthquakes that get deeper as the ocean plate descends further, defining a zone of earthquake foci known as a Benioff zone.

Continued subduction of the South American Plate brings sea water, locked in the ocean crust, deep into the mantle. As the plate heats up the water is liberated, lowering the melting point of the mantle and causing partial melting. This produces magma, which rises and may be erupted explosively as andesite at the surface.

Andesitic magma is less dense than the surrounding material, and can have a temperature of 1000 o C. It is viscous, trapping gases as it rises. The water and gases in andesitic magma account for the explosive activity of andesitic volcanoes, which typically lie dormant for many hundreds or thousands of years. These volcanoes typically produce ash and pyroclastic flows, as well as small amounts of andesitic lava.

The eruptions on Montserrat during the 1990s are a good example of this type of activity.

The Caribbean volcanic islands form a curved linear chain or 'volcanic island arc' parallel and to the west of the Puerto Rico Trench.

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An online resource from the Geological Society, outlining the three types of plate boundary and the activity that characterises them.

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An online resource from the Geological Society, outlining the three types of plate boundary and the activity that characterises them.

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Classzone.com has been retired and is no longer accessible. Because of the age of this application, the programs supported by this platform are not able to benefit from the technological improvements in accessibility, security, and HMTL5 (non-Flash) that we have incorporated into our newer programs and platforms in recent years.

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By analyzing radioactive minerals in igneous rocks, scientists can tell how much time has passed since rocks solidified from lava. This amount of time defines the age of a rock. This image shows the age of rocks on the Atlantic Ocean seafloor.

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Another difference in P and S waves is their speed. You saw that P waves travel faster than S waves. Also, P waves travel faster through solids than through liquids. Thus, the difference in the amount of time it takes for P and S waves to travel through Earth's interior provides information about the type of material through which the waves pass.

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Subduction Animation - Earthguide Online Classroom

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Subduction produces lines of volcanoes over the subducting plate, parallel to the trench and perpendicular to the direction of plate motion. The types of volcanoes associated with subduction are composite volcanoes, also called stratovolcanoes They occur high in elevationl as parts of major mountain ranges. Volcanic activity is violent and hazardous.

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Evidence for joined continents in the past

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Evidence for joined continents in the past

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This image shows a reconstruction of South America and Africa, joined together along their matching coastlines. In addition, several other pieces of evidence support the idea that the continents were joined.