Question

• Describe the 4 types of volcanoes and how are they formed?
@dtan5457

Answer 1

@dtan5457

Answer 2

please help!

Answer 3

i think this question would go under science but hold on

Answer 4

ok thx :)

Answer 5

The four types are cinder cone, shield, lava dome and composite / stratovolcano. A caldera is a sub-type of stratovolcano.

(1) Cinder cones / spatter cones -- The simplest type of volcano. They are built from particles and blobs of congealed lava ejected from a single vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a thousand feet or so above their surroundings. The common order of events for formation of a cinder cone is: eruption, formation of cone and crater, and lava flow. During 9 years of activity, beginning in 1943, Parícutin in Mexico built a prominent cone, covered about 100 square miles with ashes, and destroyed the town of San Juan.

(2) Composite / stratovolcanoes -- Many of the most famous mountains are actually stratovolcanoes. They are typically steep-sided, symmetrical cones of large dimension built of alternating layers of lava flows, volcanic ash, cinders, blocks, and bombs rising thousands of feet above their base. Some of the most conspicuous of these include Mount Fuji in Japan, Mount Cotopaxi in Ecuador, Mount Shasta in California, Mount Hood in Oregon, and Mount St. Helens and Mount Rainier in Washington. Most composite volcanoes have a crater at the summit which contains a central vent or a clustered group of vents. Lavas either flow through breaks in the crater wall or issue from fissures on the flanks of the cone. Lava, solidified within the fissures, forms dikes that act as ribs which greatly strengthen the cone like steel rebar in concrete. The *essential feature* of a composite volcano is a *conduit system* through which magma from a reservoir deep in the Earth's crust rises to the surface. The volcano is built up by the accumulation of material erupted through the conduit and increases in size as lava, cinders, ash, etc., are added to its slopes.

The variation of the composite volcano can be seen at Crater Lake in Oregon. Approximately 6,800 years ago, a large volcano (we call it Mt. Mazama) blew its top. Enormous volumes of volcanic ash and dust were expelled and swept down the slopes as ash flows and avalanches. These large-volume explosions rapidly drained the lava beneath the mountain and weakened the upper part. The top then collapsed to form a large depression, which later filled with water and is now completely occupied by beautiful Crater Lake. A last gasp of eruptions produced a small cinder cone, which created Wizard Island near the rim of the lake. Calderas can be huge, but they are not technically a type of volcano.

(3) Shield volcano -- Shield volcanoes, the third type of volcano, are built almost entirely of fluid lava flows. Flow after flow pours out in all directions from a central summit vent, or group of vents, building a broad, gently sloping cone of flat, domical shape, with a profile much like that of a warrior's shield (hence the name). They are built up slowly by the accretion of thousands of highly fluid lava flows (usually basalt) that spread widely over great distances, and then cool as thin, gently dipping sheets. Lavas also commonly erupt from vents along fractures (rift zones) that develop on the flanks of the cone. The Hawaiian Islands are composed of linear chains of these volcanoes including Kilauea and Mauna Loa on the island of Hawaii-- two of the world's most active volcanoes. In some other shield eruptions, basaltic lava pours out quietly from long fissures instead of central vents and floods the surrounding countryside with lava flow upon lava flow, forming broad plateaus. Lava plateaus of this type can be seen in Iceland, southeastern Washington, eastern Oregon, and southern Idaho. Along the Snake River in Idaho, and the Columbia River in Washington and Oregon, these lava flows are exposed and measure more than a mile in total thickness.

(4) Lava domes -- Lava domes are formed by relatively small, bulbous masses of lava too viscous to flow any great distance; consequently, on extrusion, the lava piles over and around its vent. A dome grows largely by expansion from within. As it grows its outer surface cools and hardens, then shatters, spilling loose fragments down its sides. Some domes form craggy knobs or spines over the volcanic vent, whereas others form short, steep-sided lava flows known as "coulees." Volcanic domes commonly occur within the craters or on the flanks of large composite volcanoes. A portion of Katmai, Alaska, Mont Pelée in Martinique, Lesser Antilles, and Lassen Peak and Mono domes in California are examples of lava domes. Mount St. Helens has been repeatedly building small lava domes in its crater ever since its eruption in 1980.

Answer 6

thanks ! Do you know science? Can you help me with science questions please? ?:)

Answer 7

sure i can try

Answer 8

ok thx :)

Answer 9

shoot for it

Answer 10

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