Lab Lesson 2 Essay

This lab uses earthquake data to construct profiles of two convergent boundaries: the Tonga Trench and the Peru-Chile Trench. Where two tectonic plates converge, if one or both of the plates is an oceanic lithosphere, a subduction zone will form. When crust is formed at a mid-ocean ridge, it is hot and buoyant meaning it has a low density. As it spreads away from the ridge and cools and contracts, or becomes denser, it is able to sink into the hotter underlying mantle. When two oceanic plates collide, the younger of the two plates, because it is less dense will ride over the edge of the older plate. The density of the

There are three different types of plate boundaries. The first type of plate boundaries is, the spreading boundary. A spreading boundary is when two plates move apart. The spreading boundary is also known as a divergent boundary. The second type of plate boundary is a colliding boundary. A colliding boundary is when two plates come together, or collide. It is also known as convergent boundary. The third is, a sliding boundary. A sliding boundary is when two plates slip past each other moving in opposite directions. It is also known as transform boundary. Those were the three different types of plate

The plate tectonics theory was made by a German named Alfred Wegener. He stated that a single continent existed about 300 million years ago named Pangaea and that it split into two continents of Laurasia in the north and Gondwanaland in the south. Today’s continents were formed by further splitting of the two masses.

The new volcanic material welling up into the void, which forms a ribbon of new materials and breaks down its center gradually, when the plates move apart from the axis of the mid-oceanic ridge system. Therefore, every separating plate accretes one half a ribbon of new lithosphere, and, thus, a new surface is added (Pitman, W.C, 2007). The process is continuous, and separation is always happening at the

The youngest oceanic crust is located along the mid-ocean ridges where new crust is formed when the old crust is pushed away from mid – ocean ridges as a result of the seafloor spreading.

As the crust moves away from the volcanoes and cools and becomes less dense and breaks up.

The Earth’s outer crust is made up many tectonic plates that move over the surface of the planet. When the plates come collide, volcanoes will form sometime (National Ocean Service). Volcanoes can also form in the middle of a plate, where magma rises upward until it erupts on the sea floor, at what is called a “hot spot” (National Ocean Service). A hot spot is a plume of magma or molten rock that rises from within the Earth then reaches the surface forming underwater volcanoes which may grow tall enough to

began to flow along weak layers that define the folds and faults and carved the resistant

2. What was the first line of evidence that led early investigators to suspect that the continents were once connected?

7. What is the relationship between plate tectonics and the ocean floor—seafloor spreading, for example?

Some examples of this kind of plate boundary are, oceanic-oceanic or oceanic continental convergent boundaries which can both lead to the formation of trenches in the ocean. Continental-Continental divergent plates happen when two continental plates pull apart from another causing rock in between them to drop deeper and deeper and if it drops low enough it may be filled with water. Oceanic-oceanic divergent two plates are pushed apart by the continual expansion of magma at the mid-ocean ridge causing it to expand and subdue underneath another plate and

In the middle of the eighteenth century, James Hutton proposed a theory, uniformitarianism; “the present is the key to the past”. It held that processes such as geologic forces- gradual and catastrophic-occurring in the present were the same that operated in the past. (Matt Rosenberg, 2004) This theory coincides with the theory of Continental Drift that was first proposed by Abraham Ortelius in December 1596, who suggested that North, South America, Africa and Eurasia were once connected but had been torn apart by earthquakes and floods. He also discovered that the coasts of the eastern part of South America and the

Heat emission from subduction zones can take many forms, such as volcanoes, geysers and hot springs. When lateral plate movement induced gaps occur between plates, collisions occur between other plates. This results in partial plate destruction. This causes mass amounts of heat to be produced due to frictional forces and the rise of magma from the mantle through propagating lithosphere fractures and thermal plumes sometimes resulting in volcanism. During plate movement, continental plates are constantly being consumed and produced changing plate boundaries.

Subduction zones are sites of convective downwelling of Earth’s lithosphere, which provides the dominate force of the driving force for mantle convection. It is through subducted slabs that oceanic crust and sediments, including volatile compounds are recycled back into mantle. Studying subduction slab is one of the most important parts of studying lithosphere dynamics. There have been a number of recent reviews of subduction zones with some specifically focusing on seismology, the mantle wedge, phase changes, the fate of slabs and water in mantle. However, in this review, I attempt to provide a broad summary that emerges from recent observations and model of subduction. Our understanding of the geometry and composition of subducted slabs, as well as the physical process of subduction, comes from indirect observation including earthquake seismology, gravity, topography, geochemistry, and petrology of island arc lavas. Also, numerical calculations of the dynamics of subducted slabs and slab thermal models also play an important role to test the model we build based on our observations. This review will include most of recent studies on these aspects. Finally, I will try to sum up the challenges on our future study of subduction slabs.

The direction of the convection can cause plate boundaries- opposite and away from each other will result in divergent plate boundaries and opposite but towards each