There is a convergent boundary on the west side of the United States. At a convergent boundary, two plates collide, and the denser plate is subducted. Volcanoes and earthquakes are common as a result of pressure and friction. There is also a transform boundary forming the San Andreas Fault which is between an oceanic plate subducting under a continental plate. 3.
Evidence of sea floor spreading can be found in the Atlantic, where it is believed that the North American and Eurasian plates are moving apart at a constructive plate margin. New land has been created due to the magma rising through a rift and cooling quickly on the surface, also creating a ridge of volcanoes called the Mid-Atlantic ridge. The
He suggested that at the centre of oceans, molten material would rise from the Earth’s mantle, causing new sea floor to be created, pushing the ocean floor. He also suggested that there were ocean trenches where old sea floor would then go back into the mantle, and molten. He found that these ocean trenches, the deepest parts of the ocean, were very near continental plates. Hess theorized that the action of the sea floor spreading caused continents to move apart and so this being evidence for continental drift, showing why it happened. The evidence of sea floor spreading was further supported by Vine and Drummond, who studied the magnetic pattern of the sea floor.
In this convergent boundary, the denser Nazca Plate is being subducted beneath the less dense continental lithosphere of the South American tectonic plate. As the plate descends it causes earthquakes in the Benioff zone, and volcanoes occur here because of melting of the plate in the asthenosphere. The southern end of the plate dips at a steep angle, while the northern end may be experiencing flat-slab subduction (in which the oceanic plate slides below the continental plate at a very low angle). A low angle of subduction may explain the relative lack of volcanic activity in the Northern part of Chile, compared to the extremely active southern volcanic mountains. Whereas Eyjafjallajokull is in Iceland, an MEDC.
Mt. St Hellens is positioned on a destructive plate boundary, this means that two different type of plate are moving towards each other, a denser ‘Oceanic Plate’ (Juan de Fuca Plate) is moving towards a lighter ‘Continental Plate’ (North American Plate). As the Oceanic Plate is heavier as it has a body of water on it, in this circumstance ‘Spirit Lake’ it is forced to subduct under the lighter Continental Plate. When this occurs the plates can stick, this causes a huge amount of friction, heat and pressure to build up. As Mt.
Assess the strength of relationship between tectonic processes and major landforms at the Earth’s surface. There is a range of evidence to suggest there is a strong relationship between tectonic processes and major landforms at the Earth’s surface due to, for example, the presence of volcanoes, fold mountains, trenches, and ridges. Tectonic processes include, divergence, which is when plates move away from each other, convergence, when plates move toward each other and collide, Subduction zones, which occur where an oceanic plate meets a continental plate and is pushed underneath, Obduction, which occurs when the continental plate is pushed under the oceanic plate, and collision boundaries, which occur where two continental plates collide and push upwards to form large mountain ranges. However this evidence is weakened by the process of weathering and erosion, due to the presence of the Grand Canyon, one of the Earth’s major landforms. As well as landforms caused by river processes, such as the Bangladesh Delta – which can be seen via satellite - therefore a major landform.
Due to high temperatures in the mantle of around 3000 degrees centigrade, this oceanic crusts melts and then rises due to the convection currents in the aesthenosphere . As it joins with trapped seawater and sediment, it melts the overlying continental crust, and the magma plumes rise to the surface. They contain more silica so are more viscous, which plugs up the volcano, meaning pressure build up. This is why these volcanoes are so explosive. Another type of plate boundary are constructive, which is the margin between two diverging plates where new magma
Saint Helen a composite volcano (or stratovolcano), a term for steep sided, often symmetrical cones constructed of alternating layers of lava flows, ash and other volcanic debris. Composite volcanoes tend to erupt explosively pose considerable danger to nearby life and property. Before 1980, snow capped, gracefully symmetrical Mt. Saint Helens was known as the “Fujiyama of America.” Mt. Saint Helens, other active Cascade volcanoes, and those of Alaska form the North
What is "summit deflation"? (page 94, para 2 to page 95) Summit deflation, which is measured by tilt meters in parts per million, is when the slope of a volcano changes usually relatively prior to an eruption. 4. How does Kilauea's magma move upward
Mt Kosciusko Field Trip Report Geological History of the Australian Alps The geological history of the Australian Alps starts when the majority of east Australia was submerged underwater at around 800 million years ago. At this time there were large sediment layers that covered the sea floor. By around 450 million years ago, the earth began to move underneath the continental plate causing uplifting and folding (Australian Alps National Parks, 2010, Geology and geomorphology of the alpine landscape para.6). Magma rose up through the layers at temperatures reaching up to 1000°C. The magma that reached the sea bed due to weakness in the crust cooled quickly and formed a layer of basalt above the sediments (see diagram 1).