Presentation on theme: "Objective: Identify the types of plate boundaries and the land features and geologic events that each feature makes."— Presentation transcript:
Objective: Identify the types of plate boundaries and the land features and geologic events that each feature makes.
Transform boundaries exist where two plates slide past each other. No lithosphere is created or destroyed Most transform faults are found on the ocean floor. Transform Boundary Transform Boundary Follow this link and draw the transform diagram on page 79.
Alpine fault in New Zealand, which forms the boundary between the Australian and Pacific plates
the Dead Sea fault, which forms the boundary between the African and Arabian plates
The San Andreas fault, which lies between the Pacific and North American plates in California. San Andreas
This occurs most commonly at mid-ocean spreading ridges. At such ridges, plates move apart and the mantle exposed is melted by the decrease in pressure, becoming magma. That magma then rises up to “fill in” as new oceanic crust. As the plates separate, the geologic feature known as a “rift valley” is created. Divergent Boundary Follow this link and draw the divergent boundary on page 81. Divergent Boundary Divergent boundaries exist where two plates are moving apart.
Iceland, which sits on the Mid-Atlantic ridge, is splitting apart on the divergent boundary between the North American and Eurasian Plates.
East African Rift Valley system marks the boundary between two plates: the Nubian plate to the west and the Somalian plate to the east. The rift valley is a classic example of a divergent plate boundary. Rift Valley
Oceanic-Oceanic Convergence: If the plates moving toward each other are both made of oceanic crust, one of the plates will move downward, or subduct, under the other plate. This is called a subduction zone. A deep trench forms on the ocean floor at the location where one oceanic plate subducts under another. Also, a volcanic arc (a chain of volcanoes parallel to the trench) typically develops above the subduction zone. These volcanoes are generated as water brought down on the subducting plate melts the overlying mantle, causing magma to rise through the mantle and crust, erupting at the surface. Old crust is destroyed at an oceanic-oceanic boundary. Oceanic-Oceanic Boundary Follow this link and draw the oceanic-oceanic convergent boundary diagram on page 82 in your IAN. Oceanic-Oceanic Boundary
The Marianas trench and volcanic arc mark where the Pacific and Philippine plates converge. Marinas Trench The Aleutians, Japan, and the Philippines are other examples of volcanic arcs that exist as a chain of islands.
If one plate topped by oceanic crust moves toward another topped by continental crust, the more dense, oceanic plate will subduct under the less dense, continental plate and a trench will develop off the shore of the continent. Old crust is destroyed at this type of boundary Oceanic-Continental Boundary Follow this link and draw the oceanic-continental convergent boundary diagram on page 82 in your IAN. Oceanic-Continental Boundary
Off the coast of South America, along the Peru-Chile trench, the oceanic Nazca Plate is being subducted beneath the continental South American Plate. As a result, the Andes, a mountainous volcanic arc, have developed in South America. The Cascade Range, where Mt. St. Helens is found, is another example of a volcanic arc formed by the convergence of oceanic and continental plates.
If both converging plates carry continental crust, neither of the plates fully subduct. Continental rocks have a relatively low density and, like two colliding icebergs, usually resist downward motion. During a collision, the crust is compressed and subjected to very high temperatures and pressures. The lithosphere thickens and crustal rocks are folded and faulted. Large amounts of uplift push rock high into the sky, forming mountain ranges such as the Alps or the Himalayas. Formation of the Himalayas