Continental Drift + Plate Tectonics Notes 1.31.12
Plate Boundaries Notes:
-Divergent
-Plates pull apart
-Mid-ocean ridge
-Magma comes up from the mantle
-rift valley
-Example: Iceland
-Divergent
-Plates pull apart
-Mid-ocean ridge
-Magma comes up from the mantle
-rift valley
-Example: Iceland
New oceanic crust forms at rift valleys, where two plates diverge or pull away from each other. Hot, molten rock from deep within the Earth called magma oozes out from cracks along these rifts and hardens to form new crust. When magma reaches the surface of the Earth, it is called lava. Over time, the lava builds up and forms huge underwater mountain ranges along the ocean's floor. The mountain ranges are called mid-ocean ridges. When the mid-ocean ridge actually builds up enough height to extend above the water's surface, it forms an island. Iceland is an example of such an island.Located at a diverging plate boundary between the North American and Eurasian plates, Iceland is a part of the Mid-Atlantic Ridge, which is part of the longest mountain chain on Earth. New crust oozes out daily at the Mid-Atlantic Ridge. For the last 250 million years, Europe has slowly pushed away from North America, causing the Atlantic Ocean to grow wider as new crust has been added to each plate. This type of boundary is called constructive since it actually builds new material onto the edges of the plates.
When two continental plates diverge, a valleylike rift develops. This rift is a dropped zone where the plates are pulling apart. As the crust widens and thins, valleys form in and around the area, as do volcanoes, which may become increasingly active. Early in the rift formation, streams and rivers flow into the low valleys and long, narrow lakes can be created. Eventually, the widening crust along the boundary may become thin enough that a piece of the continent breaks off, forming a new tectonic plate. At this point, water from the ocean will rush in, forming a new sea or ocean basin in the rift zone.
When two continental plates diverge, a valleylike rift develops. This rift is a dropped zone where the plates are pulling apart. As the crust widens and thins, valleys form in and around the area, as do volcanoes, which may become increasingly active. Early in the rift formation, streams and rivers flow into the low valleys and long, narrow lakes can be created. Eventually, the widening crust along the boundary may become thin enough that a piece of the continent breaks off, forming a new tectonic plate. At this point, water from the ocean will rush in, forming a new sea or ocean basin in the rift zone.
-Convergent Boundary
-Subduction: plate pushing under another
-Denser plate pushes under other plate
-Island Arc
-Example: Aleution Islands in Alaska
-Ocean<---->Ocean
-Ocean volcanoes
-Ocean<---->Continent
-Continent<---->Continent
Just as some plates are diverging or moving away from each other, other plates are converging or moving towards each other. The types of crust at their leading edge determine the result of the converging motion. There are three types of convergent plate boundaries:
-Subduction: plate pushing under another
-Denser plate pushes under other plate
-Island Arc
-Example: Aleution Islands in Alaska
-Ocean<---->Ocean
-Ocean volcanoes
-Ocean<---->Continent
-Continent<---->Continent
Just as some plates are diverging or moving away from each other, other plates are converging or moving towards each other. The types of crust at their leading edge determine the result of the converging motion. There are three types of convergent plate boundaries:
- continental/continental
- oceanic/continental
- oceanic/oceanic
At some convergent boundaries, an oceanic plate collides with a continental plate. Oceanic crust tends to be denser and thinner than continental crust, so the denser oceanic crust gets bent and pulled under, or subducted, beneath the lighter and thicker continental crust. This forms what is called a subduction zone. As the oceanic crust sinks, a deep oceanic trench, or valley, is formed at the edge of the continent. The crust continues to be forced deeper into the earth, where high heat and pressure cause trapped water and other gasses to be released from it. This, in turn, makes the base of the crust melt, forming magma.
The magma formed at a subduction zone rises up toward the earth's surface and builds up in magma chambers, where it feeds and creates volcanoes on the overriding plate. When this magma finds its way to the surface through a vent in the crust, the volcano erupts, expelling lava and ash. An example of this is the band of active volcanoes that encircle the Pacific Ocean, often referred to as the Ring of Fire.A subduction zone is also generated when two oceanic plates collide — the older plate is forced under the younger one — and it leads to the formation of chains of volcanic islands known as island arcs. Examples include the Mariana Islands in the western Pacific Ocean and the Aleutian Islands, off the coast of Alaska.Since the collision and subduction of plates is not a smooth process, large, powerful earthquakes are another phenomenon that result from this type of interaction. Earthquakes generated in a subduction zone can also give rise to tsunamis. A tsunami is a huge ocean wave caused by a sudden shift on the ocean floor, such as an undersea earthquake. If the wave reaches land, it can cause incredible destruction, like the Asian Tsunami, which killed more than 200,000 people in 11 countries across the Indian Ocean region in December 2004.
The magma formed at a subduction zone rises up toward the earth's surface and builds up in magma chambers, where it feeds and creates volcanoes on the overriding plate. When this magma finds its way to the surface through a vent in the crust, the volcano erupts, expelling lava and ash. An example of this is the band of active volcanoes that encircle the Pacific Ocean, often referred to as the Ring of Fire.A subduction zone is also generated when two oceanic plates collide — the older plate is forced under the younger one — and it leads to the formation of chains of volcanic islands known as island arcs. Examples include the Mariana Islands in the western Pacific Ocean and the Aleutian Islands, off the coast of Alaska.Since the collision and subduction of plates is not a smooth process, large, powerful earthquakes are another phenomenon that result from this type of interaction. Earthquakes generated in a subduction zone can also give rise to tsunamis. A tsunami is a huge ocean wave caused by a sudden shift on the ocean floor, such as an undersea earthquake. If the wave reaches land, it can cause incredible destruction, like the Asian Tsunami, which killed more than 200,000 people in 11 countries across the Indian Ocean region in December 2004.
-Transform Boundary
-Friction, pressure
-Earthquakes
-Side By Side
-Example: Ring of Fire
-Edge of Pacific Plate
-Fault Line: line where there is a build up of plate
-Example: San Andreas Fault Line in California
-Hotspot: magma is being produced, and when plate move over the magma, islands are created
-Friction, pressure
-Earthquakes
-Side By Side
-Example: Ring of Fire
-Edge of Pacific Plate
-Fault Line: line where there is a build up of plate
-Example: San Andreas Fault Line in California
-Hotspot: magma is being produced, and when plate move over the magma, islands are created