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 is a shield volcano wide?
The great width of these volcanoes relative to their height is the result of the low viscosities of erupted lavas that produce thin widespread lava flows, eruptions from both the summit and fissure vents on the volcano's flanks, and widening and subsidence along the summit and rift zones.
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. These volcanoes can be massive.
How does a shield volcano differ from a composite volcano?
What is the main difference between a shield volcano and a composite volcano? The main difference between the two is that a shield volcano is composed of basaltic lava while a composite volcano is composed of andesitic magma.
Why do shield volcanoes have broader shape and cover a large surface area?
The basaltic lava that creates shield volcanoes gives it a different shape compared to other volcanoes. It flows quickly and covers more ground, which gives the shield volcano a broad surface. Each time the volcano erupts, more basaltic lava flows over the hardened surface to create another layer of hardened lava.
Which volcano has a very wide base and appears more flat?
Shield Volcanoes They have a very wide base and are much flatter on the top than composite volcano.
Why do shield volcanoes tend to maintain a low profile and spread out over wide areas?
1. 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.
Why are shield volcanoes so wide with such low gradient slopes?
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. These flank vents are the result of the widening and / or subsidence of the volcano.
Why do volcanoes differ in size?
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 are the main differences between shield and composite volcanic cones?
Composite Cones have a conduit system through which material moves, and they are made of layers of rock, ash, and lavas. Shield Cones erupt from the central vent or from 2-3 rift zones around the central rift, and they have gentle slopes of overlapping lava flows.
Why do composite volcanoes have steeper slopes than shield volcanoes?
This is because they are formed by alternating layers (strata) of magma and ash (Figure below). The magma that creates composite volcanoes tends to be thick. The steep sides form because the lava cannot flow too far from the vent. The thick magma may also create explosive eruptions.
What are the characteristics of a shield volcano?
Shield volcanoes are characterized by broad, gently sloping flanks and a dome shape that resembles an ancient warrior's shield. These volcanoes are built almost entirely of layers of solidified basaltic lava flows.
How does the composition and viscosity of lava flows 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 are mostly formed from thick, viscous, andesitic composition lava whereas shield volcanoes are formed from runny, less viscous, basaltic composition lava.
How do volcanoes get bigger?
They grow largely by expansion from within. As fresh magma fills the inside, the cooler and harder outer surface shatters and spills hot rock and gases down the mountainside. The circle-shaped Novarupta Dome that formed during the 1912 eruption of Katmai Volcano, Alaska, measures 800 feet across and 200 feet high.
Why do shield volcanoes have very gentle slopes?
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. These flank vents are the result of the widening and / or subsidence of the volcano.
Which type of volcanic mountain has wide gentle slopes?
Where a volcano produces low viscosity, runny lava, it spreads far from the source and forms a volcano with gentle slopes: a shield volcano. Most shield volcanoes are formed from fluid, basaltic lava flows. Mauna Kea and Mauna Loa are shield volcanoes.
Why are volcanoes different sizes?
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.
When contrasting lava from a composite volcano to lava from a shield volcano?
When contrasting lava from composite volcanoes to lava from shield volcanoes, composite volcanoes most often produce silica-rich lavas with high viscosities, whereas shield volcanoes produce basaltic lavas with low viscosities.
Why do volcanoes have different shape?
Volcanoes have several shapes, which are controlled by the composition of the magma and the nature of its eruption. If a volcano produces very fluid lava (low in the compound SiO2, or silica), the magma flows a long distance before it cools, making a flat, shield-shaped volcano.
How do composite shield and cinder cone volcanoes differ?
Composite volcanoes are explosive, towering giants. Shield volcanoes quietly produce broad, massive structures through lava flows. Cinder cone volcanoes are the smallest and simplest, but still pack a volcanic punch.
Why are shield and composite volcanoes different shapes?
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.