Plate Tectonics - Oceanography

Mountain

A high, large mass of earth and rock that rises above the earth's surface with steep or sloping sides.

Trench

A steep sided depression in the ocean floor

Two oceanic plates colliding

A subduction zone is also generated by this. The older plate is forced under the younger one, and it leads to the formation of chains of volcanic islands known as island arcs.

Volcano

A vent in the earth's surface through which magma and gases erupt

Convergent Boundary: Continental - continental

Mountain ridges are created by convergent boundaries of continental and continental crust

subduction zone

The area where one plate is being pulled under the edge of another

Pangaea

The continents of Earth were clustered together in formation that the scientist Alfred Wegener had named.

Outer core

The layer of earth that is the only liquid layer

Convergent Boundary

If two plates are pushing towards each other.

Volcanic arc

An arc-shaped chain of volcanoes formed above a subduction zone.

Transform Boundary

If two plates are sliding past each other

Continental crust

The earth's crust that makes up the continents

Lithosphere

- Made up of the crust and a tiny but of the upper mantle

Convergent Boundary: ocean - continental

Deep ocean trenches and Volcanoes are created by convergent boundaries of oceans and continental crust

Magma

Molton rocks, gases, and solid crystals and minerals

Boundary

The place where the two plates meet. Boundaries have different names depending on how the two plates are moving in relationship to each other.

Theory of Plate Tectonics

Wegener theorized that pangaea was split apart and the different landmasses, or continents, drifted to their current locations on the globe.

At Convergent Boundaries

tectonic plates collide with each other. The events that occur at these boundaries are linked to the apes of plates (oceanic or continental) that are interacting

Asthenosphere

the plates of the lithosphere move (or float) on this hot, malleable semi liquid zone in the upper mantle, directly underneath the lithosphere

Convergent Boundary: ocean- ocean

Deep ocean trenches, island arcs, and subduction zones are created by convergent boundaries of ocean and ocean crust

Divergent Boundary

If two plates are moving apart from each other

Subduction Zone

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 subduct, beneath the lighter and thicker continental crust. 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.

Collision of two continental plates

Because the rock making up continental plates is generally lighter and less dense than oceanic rock, it is too light to get pulled under the earth and turned into magma. Instead, a collision between two continental plates crunches and folds the rock at the boundary, lifting it up and leading to the formation of mountains

At a divergent Boundaries

ectonic plates are moving away from each other. One result of huge masses of crust moving apart is seafloor spreading. This occurs when two plates made of oceanic crust pull apart. A crack in the ocean floor appears and then magma oozes up from the mantle to fill in the space between the plates, forming a raised ridge called a mid-ocean ridge. The magma also spreads outward, forming new ocean floor and new oceanic crust. When two continental plates diverge, a valley-like 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 divergent boundary may become thin enough that a piece of the continent breaks off, forming a new tectonic plate.

At transform boundaries

tectonic plates are not moving directly toward or directly away from each other. Instead, two tectonic plates grind past each other in a horizontal direction. This kind of boundary results in a fault. A fault is a crack or fracture in the earth's crust that is associated with this movement. Transform boundaries and the resulting faults produce many earthquakes because edges of tectonic plates are jagged rather than smooth. As the plates grind past each other, the jagged edges strike each other, catch, and stick, "locking" the plates in place for a time. Because the plates are locked together without moving, a lot of stress builds up at the fault line. This stress is released in quick bursts when the plates suddenly slip into new positions. The sudden movement is what we feel as the shaking and trembling of an earthquake. The motion of the plates at a transform boundary has given this type of fault another name, a strike -slip fault. The best-studied strike-slip fault is the San Andreas Fault in California.