The Cascade Range, which extends northward from California into British Columbia in Canada, rests on the North American Plate. The North American plate moves in a southward direction. The adjacent Pacific Plate, which is an oceanic plate, moves northward along the North American Plate, resulting in a subduction zone, in which the Pacific Plate is pushed upwards into the North American Plate, pushing up the Cascade Range. (Abbott, P.L., 2014) The frequent volcanic eruptions in the Cascade Range evidence the continued active subduction activity in this area. Subduction, in this case, pushes the older oceanic crust back into the mantle. In the Cascades range, this occurs as subduction of three smaller tectonic plates: the Juan de Fuca, Explorer and Gorda Plates. These are believed to be remnants of a much larger plate that broke apart. These smaller plates continue to slide underneath North America at a rate of approximately 3.5 centimeters per year. As these oceanic plates slide under the continental plate of North America, they dip at a sharp angle, meaning as the plates go deeper into the continental plate, they get hotter. …show more content…
On one side of this spreading ridge, new Pacific Plate crust is formed, which then moves away from the ridge. One the other side of this ridge is the Juan de Fuca Plate and Gorda Plate, both of which move eastward towards the North American plate.
The Juan de Fuca Plate sinks beneath the North American Plate at a rate of 3-4 centimeters per year and as long as the subduction continues, new Cascade volcanoes will continue to
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada: Cambridge University Press, 354 p., p. 158-160, Contribution by Patrick Pringle.
The west coast of the islands is on the edge of a continental shelf created by ancient volcanic movement (Broadhead 5) .This volcanic activity is due to plate tectonic movement which also created the numerous amounts of earthquakes on the island. Compared to the rest of British Columbia, Haida Gwaii has the most earthquake activity (Broadhead 5), the last of which being in a magnitude of 7.7 on t...
Mauna Loa is located on a hot spot in the Pacific Ocean. It is not near a plate boundary, in fact it is 3,200 km from the nearest plate boundary, and is situated in the middle of the Pacific tectonic plate. This is actually a rarity, as 90% of volcanoes are along a tectonic plate boundary. A hot spot occurs where long, stationary vertical pools of magma rise up and towards the plate. Movement of the tectonic plates above the hot spot created Mauna Loa, along with the other Hawaiian volcanoes. The older Hawaiian Islands were once above this stationary hot spot, but have been carried northwest by the slowly moving Pacific plate. As the plate moves, it carries the previously formed, older, volcanoes with it, creating a trail of younger, new volcanoes behind. The islands are lined up along the Hawaiian Ridge-Emperor Seamounts chain, which is 3,750 miles and includes Kauai, Maui, Oahu and Hawai’i, from north to south, respectively. There are around 80 volcanoes in this chain; most of them underwater, consequently the term seamount refer to submarine volcanoes. Three volcanoes of Hawai’i, Mauna Loa, Kilauea and Loihi seamount, are all currently sharing the Hawaiian hot spot. Although, recent evidence has shown that all three volcanoes use have separate plumbing systems to expel the lava from the pool of magma deep below them. It has also been suggested that Loihi is slowly moving Mauna Loa from the center of the island, thus shifting directly over the hot spot. The closer to the hot spot a volcano is, the more active it will be. The Hawaiian hot spot has laid down layers of lava, building up enormous islands from the ocean floor.
Basalt forms due to the partial melting of the layer of the mantle called the asthenosphere. The asthenosphere is the plastic zone of the mantle beneath the rigid lithosphere. Mantle plumes coming from the mesosphere can cause the asthenosphere to melt with heat or even if pressure decreases, which is called decompression melting (Richard 2011). The magma that forms from this melting is mafic magma that solidifies once it reaches the earth’s surface and cools quickly. The above process mainly occurs mainly during intraplate igneous activity which is the main explanation for volcanic activity that occurs a long distance away from a plate boundary. If the tectonic plate above the mantle plume is moving it can create a string of volcanic activity such as in Hawaii. See Fig 2.
The Cascadia region has experienced several types of earthquakes and it is very likely to experienced similar quakes in the near future. Cascadia earthquakes fall into three major categories: The first type is shallow or crustal earthquakes which are caused by rupture of the faults in the North American Plate. The Scott Mills earthquake happened in 1993 and it occurred in the Willamette Valley. The second type is deep or intraplate earthquakes are caused by rupture faults within the subducting Juan de Fuca Plate, deep earthquakes are often the most damaging type of earthquakes. In 2001, a deep earthquake named the Nisqually hit the Puget Sound area of Western Washington. The third type is the Cascadia Subduction Zone earthquakes are the powerful and with the largest magnitude of 9 on the Richter scale. The Cascadia Subduction Zone is a bit more complicated than other two types of earthquakes. The zone separates the Juan de Fuca plates and the North American plate, subduction earthquakes happen when one plate is pushing beneath each other. When one of the faults ruptures, the overriding plate push upward generating frictional stress eventfully the stress reaches a critical point, a sudden failure occurs along the fault plane resulting in the “megathrust” earthquake rel...
Subduction of plates, 2002, the regents of the university of California, Viewed 12 April 2014,
Before examining the Northridge event, understanding the naturally occurring hazard that is an earthquake will help to better understand exactly what happened and why it was such an important geological event. With four distinct layers, two layers, the crust and upper portion of the mantle, compose the skin that is the surface layer of the Earth. The crust is not a single, continuous piece. It is actually several different pieces, or plates, that come together to form the puzzle that comprises the surface of the Earth. These plates are in constant motion rubbing against one another. These areas, known as fault lines, where the plates rub up against one another have spots where one plate ”gets stuck while the rest of the plate keeps moving. When the plate has moved far enough, the edges unstick and is how most of the earthquakes around the world occur” (Wald, 2012). The energy stored from the friction of the two plate...
There are forty-two volcanoes in Mexico. Mexico’s volcanoes are on the North American Continental tectonic plate. Out of all the volcanoes the three most active are Popocatepetl, El Chichon, and Colima. El Chichon had its last eruption in 1982. No one living near this mountain saw it coming because its last eruption was one hundred and thirty years earlier and was minor. They also ignored the earthquake on the night of March twenty-eighth. But in the morning no one could miss the ash and debris in the air. Most of the two thousand people that died, died from breathing in the harmful gases. It cooled the whole earth the following year. When it erupted in 1982 it created a three hundred meter deep crater. Before the eruption in 1982 El Chichon
Forty-eight years ago, Dan McKenzie graced us with his first paper on the “viscosity of the lower mantle”, or better known as the theory of plate tectonics. This theory states that the Earth is broken up in to plates that move in all different directions and speeds. The movement is caused by convection in the asthenosphere. The lower and hotter magma rises to the top and pushes the plates outwards, then cools and sinks. Also, in places like the Mid-Ocean Ridge, there are breaks in the Earth’s crust where magma comes up and replaces old rocks pushing them to either side. (Richardson) This theory is supported by irrefutable facts. Some of which are: the shapes of many of the continents look as though they at one time were all connected, there are similar fossils on almost all of the continents, and the oldest parts of oceanic plates are only around 200 million years old. This theory is as close to fact as it gets.
The Rocky Mountains are an incredible mountain range located in North America in the Western Hemisphere. The mountain range stretches from northern Colorado and into southwestern Canada. It is home to a diverse ecosystem, both geographically and biologically and is revered as a monumental landform worldwide.
The epicenter of the earthquake in Alaska was about 10km east of the College Fiord, approximately 90km west of Valdez and 120km east of Anchorage, Alaska largest city. The earthquake was felt about 1,300,000 square kilometers away from the epicenter. (Christensen, Doug PhD.) About 30 kilometers deep, the first slip occurred under northern Prince William Sound, and an 800 kilometer rupture in the rocks extended horizontally, roughly parallel to the Aleutian trench. (Bolt) The cause of this massive earthquake was the vertical displacement of northwest motion of the Pacific plate. Also, it was estimated that about 200,000 square kilometers of the crust were deformed, making this the greatest area of vertical displacement ever measured. (Bolt)
Convection currents deep in the mantle of the earth, begin to well up towards the surface. As the pressure increases, it sets the crustal plates in motion. There are different kinds of mountains - Volcanic, Folded, Fault-block, and Dome mountains. Volcanic mountains are formed when magma comes up through cracks in the Earth’s crust and explodes out of lava and ash. The Hawaiian volcanoes, Mt. Hood, Mt. Etna, Vesuvius, and Mt. Saint Helens is an example of volcanic mountains.
Researchers have found that these caldera valleys reside near some of the largest amounts of volcanic rock we have on Earth, insinuating that the heat vents that collapsed were “monstrous.” However, very thick continental crust and a huge heat source is needed to create these supervolcanoes which makes them very rare. The last supervolcanoes to erupt in the continental U.S occurred 640,000 years ago in Yellowstone and 760,000 years ago in Long Valley, California. These eruptions occurred, like all supervolcanoes, because the pressurized magma raises overlying crust enough to create vertical breaks that spread to the surface of the
The concurrent convective circulations in the mantle leads to some segments of the mantle moving on top of the outer core which is very hot and molten in nature. This kind of movement in different segments occurs as tectonic plates. These tectonic plates are basically seven on the earth surface as major ones, although, several small ones exist also. The plates motions are characterized by varying velocities, this variance results to sub sequential collision of two plates (leading to formation of a mountain in a convergent boundary), drift of two plates (leading to formation of rifts in a divergent boundary), or parallel movement in a transform boundary(Webcache 3).
“Before plate tectonics, people had to come up with explanations of the geologic features in their region that were unique to that particular region, plate tectonics unified all these descriptions and said that you should be able to describe all geologic features as though driven by the relative motion of these tectonic plates” (Oskin). Plate tectonics is a theory that Earth’s outer shell is divided into eleven plates from the interaction of rigid lithospheric plates that move slowly over the underlying mantle. The movement of the plates is slow and is often compared to the rate at which fingernails grow. These plates all glide over a hot surface in our earth, otherwise known as the core. “The driving force behind plate tectonics is convection in the mantle. Hot material near the Earth's core rises, and colder mantle rock sinks” (Oskin). The prime example of the process of plate tectonics is the idea of the once supercontinent, Pangea, and its separation into the continents of the world today. Plate tectonics have also created and caused many features on planet Earth (other than earthquakes) such as faults, volcanoes, and mountains. For example, the Himalayan Mountains, located in Japan, are a model of causality from plate tectonics. Another example would be the volcanoes located around the Ring of