why are shield volcanoes wider than composite volcanoes


Why Are Shield Volcanoes Wider Than Composite Volcanoes?

Why are shield volcanoes wider than composite volcanoes? The lava that flows out of shield volcanoes is more fluid than the lava that flows out of composite volcanoes.

Why are shield volcanoes wider than composite volcanoes and not as steep?

The magma that creates shield volcanoes is less viscous, so it flows much more easily. For this reason, the eruptions of shield volcanoes are non-explosive. In addition, the less viscous lava spreads out more, which makes shield volcanoes much larger and flatter than stratovolcanoes.

Why are shield volcanoes so wide?

Shield volcanoes are formed by lava flows of low viscosity – lava that flows easily. Consequently, a volcanic mountain having a broad profile is built up over time by flow after flow of relatively fluid basaltic lava issuing from vents or fissures on the surface of the volcano.

Are shield volcanoes bigger than composite?

Composite volcanoes, also known as stratovolcanoes, are towering structures, often rising more than 10,000 feet. Shield volcanoes are broad, typically 20 times wider than they are high.

Are shield volcanoes wide?

Shield volcanoes are exactly what the nomenclature implies – very large, broad, shield-like structures that have a low aspect ratio (i.e., much wider than they are tall). These volcanoes form when a centralized vent produces low-viscosity flows over a long period of time (Walker, 2000: 284).

How are shield and composite volcanoes similar?

Composite cone volcanoes are cone-shaped volcanoes composed of layers of lava, ash and rock debris. Composite cone volcanoes can grow to heights of 8,000 feet or more and have explosive eruptions. Shield volcanoes are broad, domed-shaped volcanoes with long, gently sloped sides.

What makes a shield volcano A shield volcano?

A shield volcano is a type of volcano named for its low profile, resembling a warrior’s shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano.

Why is Kilauea a shield volcano?

Kīlauea Volcano, Hawai’i. (Public domain.) Lava flows finally began to erupt again about 1,000 years ago, breaking the 1,200-year-long interval dominated by explosive eruptions. Lava completely filled the summit caldera, then overflowed to form a new shield—the Observatory shield—in place of the caldera.

Why do shield volcanoes have thin lava?

Shield volcanoes consist largely of thin lava flows, with minor pyroclastic (mainly ash) layers. … The gentle slopes are the result of the low lava viscosity, allowing lavas to flow fast and far. The lava flows (pahoehoe and aa) commonly initiate their path from flank vents and fissures rather than from the summit.

How are shield volcanoes shape?

Shield volcanoes

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.

Why do shield volcanoes have such a different shape than stratovolcanoes?

Why do shield volcanoes have such a different shape than stratovolcanoes? vent and tumble to form slopes of about 30 degrees; they build the cone higher near the vent. … Why do the Hawaiian Islands form a chain of volcanoes? An active hotspot volcano lies in the ocean basin near the Hawaiian Islands.

Why are some volcanoes cone shaped and shield shaped?

Shield cones were named by Icelandic people because the cone’s shape reminded them of a warriors shield layed down. Shield cones form from hot, runny lava that is erupted from the the volcano through its summit and the many side vents and fissures throughout the volcano’s flanks (Sides).

What are the differences between shield volcanoes and stratovolcanoes?

Stratovolcanoes have relatively steep sides and are more cone-shaped than shield volcanoes. They are formed from viscous, sticky lava that does not flow easily. … Stratovolcanoes are more likely to produce explosive eruptions due to gas building up in the viscous magma.

Why do shield volcanoes tend to maintain a low profile and spread out over wide areas?

Why do shield volcanoes tend to maintain a low profile and spread out over wide areas? Their eruptions are more forceful than other volcanoes, which spreads the lava and ash further away. Their lava is very fluid so it spreads across the land instead of piling up high.

What is the composition of a shield volcano?

Shield volcanoes are composed almost entirely of relatively thin lava flows built up over a central vent. Most shields were formed by low viscosity basaltic magma that flows easily down slope away form the summit vent.

How does a composite volcano form?

Composite cone volcanoes are also called stratovolcanoes. They form when different types of eruptions deposit different materials around the sides of a volcano. Alternating eruptions of volcanic ash and lava cause layers to form. Over time these layers build up.

What do shield volcanoes and composite volcanoes have in common?

Shield volcanoes erupt quietly. … Explosive stratovolcanoes, or composite volcanoes, have steep, symmetrical, conical shapes built up over time by alternating layers of lava flows, volcanic ash, cinders and other volcanic particles. A central vent or cluster of vents is at the summit.

How are shield and composite volcanoes formed?

Composite volcanoes are usually found at destructive plate margins. Examples of composite volcanoes include Mount Fuji (Japan), Mount St Helens (USA) and Mount Pinatubo (Philippines). Shield volcanoes are low with gently sloping sides and are formed from layers of lava. Eruptions are typically non-explosive.

Why are composite cones steeper than Shields?

A shield volcano is relatively flat, and a composite volcano is relatively steep because of the type of magma that creates them.

What is the characteristics of shield volcano?

Shield volcanoes have the following characteristics: Basaltic magma, which is high in temperature, very low on silica and with low gas content. This type of magma produces fluid lava with very little explosive activity. Basic lava, which is non-acidic and very runny.

How does a shield volcano erupt?

Eruptions at shield volcanoes are only explosive if water somehow gets into the vent, otherwise they are characterized by low-explosivity fountaining that forms cinder cones and spatter cones at the vent, however, 90% of the volcano is lava rather than pyroclastic material.

What is lava shield?

n. (Geological Science) a broad volcano built up from the repeated nonexplosive eruption of basalt to form a low dome or shield, usually having a large caldera at the summit.

Are shield volcanoes explosive?

Shield volcanoes are built by many layers over time and the layers are usually of very similar composition. The low viscosity also means that shield eruptions are non-explosive. Eruptions tend to be mild in comparison to other volcanoes, but lava flows can destroy property and vegetation.

Why do shield volcanoes have weak eruptions?

Shield volcanoes have weak eruptions because the material that comes out of a volcano has low viscosity.

What is the size of Kilauea volcano?

1,247 m

How does the composition temperature and viscosity of lava differ between composite volcanoes and shield volcanoes?

How does the composition and viscosity of lava flows differ between composite volcanoes and shield volcanoes? Composite volcanoes tend to have intermediate to felsic lava that is very viscous whereas shield volcanoes have basaltic lava that is low in viscosity.

Where do most shield volcanoes form quizlet?

Shield volcanoes mostly occur at divergent boundaries. Specifically, they can occur in rift valleys and mid-ocean ridges, which all form at divergent boundaries themselves. They also form at hotspots.

Do composite volcanoes have high or low viscosity?

The volcanoes form steep cones, rather than rounded shapes, because the magma is viscous. Composite volcano magma is felsic, which means it contains silicate-rich minerals rhyolite, andesite, and dacite. Low-viscosity lava from a shield volcano, such as might be found in Hawaii, flows from fissures and spreads.

Where do most shield volcanoes form on the ocean floor or on the continents?

Shield volcanoes usually form above a hot spot in the ocean floor. The magma that feeds these volcanoes is from the upper mantle. Composite volcanoes (stratovolcanoes) form in subduction zones where an oceanic plates subducts beneath a continental plate. They form towering volcanoes like Mount Rainier in Washington.

Why do volcanoes differ in size and shape?

Volcanoes come in different sizes and shapes. The overall size of a volcano is determined by the total volume of lava that has erupted. The shape of a volcano is largely determined by the type of lava that has erupted, and importantly, its viscosity. Viscosity is a fluid’s resistance to flow.

What is the shape of composite volcanoes?

conical shape
Unlike shield volcanoes, composite volcanoes have a distinctly conical shape, with sides that steepen toward the summit. Cinder cones are the smallest, and almost too small to see next to a volcano like Mauna Loa. Eve Cone is a cinder cone on the flanks of Mt.

What is one way that cinder cones differ from composite and shield volcanoes?

What is one way that cinder cones differ from composite and shield volcanoes? Cinder cones are smaller than composite and shield volcanoes.

What are the characteristics of composite volcano?

Composite volcanoes have the following characteristics:

  • Acidic lava, which is very viscous (sticky).
  • Steep sides as the lava doesn’t flow very far before it solidifies.
  • Alternate layers of ash and lava. For this reason, they’re also known as stratovolcanoes . …
  • Violent eruptions.
  • Longer periods between eruptions.

Is Kilauea a shield volcano or stratovolcano?

This is because Kilauea is a so-called shield volcano, which is typically broader in shape and has lava that is relatively fluid. On the other hand, stratovolcanoes — which include Mount Pinatubo in the Philippines and Mount St.

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