Volcanoes Flashcards

Question

Tephra

Answer 1

pieces of volcanic rock and ash that blast into the air after a volcanic eruption. larger pieces fall near the volcano, causing injury or death and destruction to structures, smaller pices can travel for thousands of kilometres, ash fall acauses poor visibility and slippery roads and roofs can fall under the weight and clog engines (disrupt air travel)

Answer 2

type of mudlow composed of slurry pyroclastic material, rocky debris and warer which flows from a volcano along a river valley with consistency and approximate density of wet concrete, destrucitve, can flow tens of metres per second over 22mph and 140m deep, e.g. lahar at Nevado del Ruiz, Colombia which killed over 23,000 people 1985

Answer 3

a type of glacial outburst flood due to heat from a volcanic eruption melting the snow and ice in a glacier, large amounts of water, rock, gravel and ice can suddenly be released catching people unaware and damaging land and infrastructure. occur anywhere where water accumulates in a subglacial lake beneath a glacier

Answer 4

A hot spot is is fed by a region deep within the Earth’s mantle from which heat rises through the process of convection. This heat facilitates the melting of rock at the base of the lithosphere, where the brittle, upper portion of the mantle meets the Earth’s crust. The melted rock, known as magma, often pushes through cracks in the crust to form volcanoes. Hot spot volcanism is unique because it does not occur at the boundaries of Earth’s tectonic plates, where all other volcanism occurs. Instead it occurs at abnormally hot centers known as mantle plumes. Scientific models depict these plumes of molten rock almost like a lava lamp, with a rising bulbous head fed by a long, narrow tail that originates in the mantle. As the plume head reaches the lithosphere, it spreads into a mushroom shape that reaches roughly 500 to 1000 kilometers (310 to 621 miles) in diameter. These features are called diapirs. Scientists have different theories about where hot spots form. The dominant theory, framed by Canadian geophysicist J. Tuzo Wilson in 1963, states that hot spot volcanoes are created by exceptionally hot areas fixed deep below the Earth’s mantle. More recent scientific studies suggest that these hot spots may be found at more shallow depths in the Earth’s mantle and may migrate slowly over geologic time rather than stay fixed in the same spot. A volcano above a hot spot does not erupt forever. Attached to the tectonic plate below, the volcano moves and is eventually cut off from the hot spot. Without any source of heat, the volcano becomes extinct and cools. This cooling causes the rock of the volcano and the tectonic plate to become more dense. Over time, the dense rock sinks and erodes. A new and active volcano develops over the hot spot, creating a continuous cycle of volcanism. Hot Spot Features Most scientists think that 40 to 50 hot spots exist around the world, although this number varies widely because of differing definitions of what a hot spot is. Major hot spots include the Iceland hot spot, under the island of Iceland in the North Atlantic; the Réunion hot spot, under the island of Réunion in the Indian Ocean; and the Afar hot spot, located under northeastern Ethiopia. Volcanic activity at hot spots can create submarine mountains known as seamounts. Some scientists estimate that seamounts make up 28.8 million square kilometers (17.9 million square miles) of the Earth’s surface, an area larger than any other habitat. Depending on the amount of volcanic activity, seamounts can rise hundreds or thousands of meters from the seafloor. The Louisville Seamount Chain, for example, is comprised of over 80 seamounts that extend in a 4,000 kilometer (2,485 mile) arc in the South Pacific Ocean, about 1,500 kilometers (932 miles) from Wellington, New Zealand. The seamounts originated from a single hot spot and have been slowly transported in a northwest direction by the Pacific plate. Hot spot seamounts that reach the surface of the water can create entire chains of islands, such as the U.S. state of Hawaii. Scientists think that this volcanic chain of islands has been forming for at least 70 million years over a hot spot underneath the Pacific plate. The Hawaiian Islands were created one right after the other as the plate moved northwest—almost like an island factory. Of all the inhabited Hawaiian Islands, Kauai is located farthest from the presumed hot spot and has the most eroded and oldest volcanic rocks, dated to be around 5.5 million years old. Meanwhile, on the “Big Island” of Hawaii, the oldest rocks are less than 0.7 million years old and volcanic activity continues to create new land. Hot spots can also develop beneath continents. The Yellowstone hot spot, for example, has produced a series of volcanic features that extend in a northeastern direction. The features stretch from the U.S. states of Idaho and Oregon, some 650 kilometers (400 miles) to northwest Wyoming. Over 16.5 million years, the hot spot has generated 15 to 20 massive eruptions that left large volcanic depressions called calderas. The McDermitt Volcanic Field, located on the Nevada-Oregon border, is the hot spot’s oldest large feature. It formed from an eruption roughly 16.1 million years ago. The active Yellowstone Caldera, in Yellowstone National Park in northwest Wyoming, is the hot spot’s youngest large feature, having last erupted just 640,000 years ago. Hot spots don't always create volcanoes that spew rivers of lava. Sometimes, the magma heats up groundwater under the Earth’s surface, which causes water and steam to erupt like a volcano. These eruptions are called geysers. A famous geyser is Old Faithful in Yellowstone National Park. When it erupts, the water is 95.6 degrees Celsius (204 degrees Fahrenheit) and can reach more than 55 meters (180 feet) high.

Answer 5

upwelling of magma within Earth's mantle A mantle plume is posited to exist where hot rock nucleates at the core-mantle boundary and rises through the Earth's mantle becoming a diapir in the Earth's crust.[3] The currently active volcanic centers are known as "hot spots". In particular, the concept that mantle plumes are fixed relative to one another, and anchored at the core-mantle boundary, was thought to provide a natural explanation for the time-progressive chains of older volcanoes seen extending out from some such hot spots, such as the Hawaiian–Emperor seamount chain.

Answer 6

Slab pull is the pulling force exerted by a cold, dense oceanic plate plunging into the mantle due to its own weight. The theory is that because the oceanic plate is denser than the hotter mantle beneath it, this contrast in density causes the plate to sink into the mantle. The process of a tectonic plate descending into the mantle is termed subduction.

Answer 7

the process by which collision of the earth's crustal plates results in one plate's being drawn down or overridden by another, localized along the juncture (subduction zone) of two plates SEE ASSESSMENT

Answer 8

the process by which collision of the earth's crustal plates results in one plate's being drawn down or overridden by another, localized along the juncture (subduction zone) of two plates SEE ASSESSMENT Wouter Schellart developed a global map showing subduction zones and found the main indicators include style of deformation in the plate overlying the subduction zone, leve l of stress, dip angle, curvature as well as rate of movement, to predict which ones are capable of giant earthquakes

Answer 9

Viscosity is a measure of a fluid's resistance to flow. It describes the internal friction of a moving fluid. A fluidwith large viscosity resists motion because its molecular makeup gives it a lot of internal friction. A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion.