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Dynamic Earth Processes: Geosphere
Transcript of Dynamic Earth Processes: Geosphere
Simplistically, the earth consists of plates, and plate boundaries, those zones where the plates contact and interact. Everything between plate boundaries are part of some plate.
Plates are combinations of two units, continents and ocean basins. Plates are composed either of a fragment of ocean basin, or (more commonly) a fragment of ocean basin with an attached continent.
The three kinds of plate boundaries are divergent, convergent, and transform.
Plates interact at these boundaries.
Divergent plate boundaries always create new ocean floor when magma oozes into the crack as plates separate. This process results in the formation of mid ocean ridges and means that the ocean basins are getting larger at divergent plate boundaries. Since the earth cannot get larger it means ocean floor must be disappearing somewhere else.
There are two types of convergent boundaries.
The first, called subduction, is if one of the plates is more dense than the other, like when oceanic and continental crust meet. The most dense plate (Oceanic) will be forced under the less dense plate (Continental).
This forms a trench, or deep valley, where the plates meet. Subduction often results in a chain of volcanoes running parallel to the trench.
In the the cases where Continent meets Continent a collision occurs, resulting in mountain formation.
At transform boundaries two plates just slide past one another horizontally. Most of these are found in the ocean basins, but the San Andreas fault in California and Mexico is an example of a continental fault.
Which of these plate boundaries results in fault zones that generate earthquakes?
What are the 4 types of faults that cause earthquakes?
The point at which the wave originates is what we call the Earthquake focus (foci plural).
Shallow earthquakes create the most damage and account for about 75% of the total seismic energy released around the world. Unlike intermediate and deep focus earthquakes, shallow earthquakes occur at all types of plate boundaries like ocean trenches, subduction zones, etc.
So what is the epicenter of an earthquake? The point on the ground surface directly above the focus is known as the epicenter
What kinds of damage result from earthquakes?
What kind of fault is the San Andreas an example of?
What kinds of equipment are used to monitor and measure earthquakes?
Since the next "big" earthquake in California is a question of when, not if...are you prepared?
What should be in your earthquake kit?
Make a detailed list of items you should have ready in case of a major natural disaster.
Because oceanic crust is created and destroyed so easily ocean basins are young. The oldest ocean crust is only about 200 million years old.
Continents, on the other hand, are composed of light weight rock and never get subducted. This makes continental rock more or less permanent. The oldest continental fragment is 3.96 billion years old, virtually as old as the earth itself.
Did you get all of that?
Review some volcanoe basics! Take the quiz at the end of the lesson, copy the questions and answers as part of your notes.
Dig a little deeper, explore the interactive features of this site. When you test your skills record the questions and answers to turn in with your notes.
Experiment with Volcanic eruptions.
Check out the playlist:
Dynamic Earth Processes:
Tectonic Plate Boundaries