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Unlike shield volcanoes, stratovolcanoes have a steep profile and periodic eruptions. Those volcanoes which may erupt again at any time are called active.The lava that flows from stratovolcanoes cools and hardens before spreading far. The magma forming this lava is often felsic, with high-to-intermediate levels of silica, and less mafic magma. Those that are now quiet called dormant (inactive).It is much bigger than Tamu – it's the size of France".
The base of the crater then sinks, leaving a caldera where the top of the volcano was before. The researchers doubted the submerged volcano's peak ever rose above sea level during its lifetime and say it is unlikely to erupt again.
Krakatoa, best known for its catastrophic eruption in 1883, is much smaller now. "The bottom line is that we think that Tamu Massif was built in a short (geologically speaking) time of one to several million years and it has been extinct since," co-author William Sager, of the University of Houston told the AFP news agency."There were lots of oceanic plateaus (that) erupted during the Cretaceous period (145-65 million years ago) but we don't see them since. The biggest oceanic plateau is Ontong Java plateau, near the equator in the Pacific, east of the Solomon Islands.
Even though their sides are not very steep, shield volcanoes can be huge. The caldera of Yellowstone Park was formed in that way; so were the Hawaiian Islands.
Mauna Kea in Hawaii is the biggest mountain on Earth if it is measured from its base on the floor of the sea. It is built up of many layers of hardened lava, tephra, pumice, and volcanic ash. A traditional way to classify or identify volcanoes is by its pattern of eruptions.
The base of the volcano increases in size over successive eruptions where solidified lava spreads out and accumulates. The second way is when a tectonic plate moves over a hot spot in the Earth's crust.
Some of the world's largest volcanoes are shield volcanoes. The hot spot works its way through the crust until it breaks through.
Mauna Loa is part of the five volcanoes on Hawaii's 'Big Island'. The largest recent eruption from Mauna Loa left a lava trail 51 kilometres (32 miles) long.
The most recent time this volcano erupted was in 1984. Like all the other Hawaiian volcanoes, Mauna Loa was created by the movement of the Pacific tectonic plate which moved over the Hawaii hotspot in the Earth's mantle. The lava and pyroclastic material (clouds of ash, lava fragments and vapor) that comes out from volcanoes can make many different kinds of land shapes. These volcanoes are formed by fluid low-silica mafic lava.
Refer to fgure 2] This heavy ash covered buildings and even caused the roofs of houses, schools and other buildings to collapse.
The ash clouds produced by volcanoes can also interfere with aviation.