Does a Strato volcano have high or low viscosity?
The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity.
Do Hawaiian volcanoes have high or low viscosity?
The high fluidity (low viscosity) of Hawaiian lavas derives mainly from its basaltic composition, characterized by more iron (Fe), magnesium (Mg), calcium (Ca), and titanium (Ti), and less silicon (Si), aluminum (Al), sodium (Na), and potassium (K), compared to such viscous lavas as the dacite erupted explosively at …
What volcanoes have high viscosity?
In contrast to shield volcanoes, there are stratovolcanoes, like Mt. St. Helens. These volcanoes produce sticky, higher viscosity magma (andesite and rhyolite) that does not travel very far.
What is the difference between Strato and shield volcanoes?
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.
What determines a magma’s viscosity?
Viscosity of Magmas Viscosity is the resistance to flow (opposite of fluidity). Viscosity depends on primarily on the composition of the magma, and temperature. Higher SiO2 (silica) content magmas have higher viscosity than lower SiO2 content magmas (viscosity increases with increasing SiO2 concentration in the magma).
Does Hawaii experience effusive or explosive volcanoes?
Effusive eruptions occur when hot, (1200oC) runny basalt magmas reach the surface. Dissolved gases escape easily as the magma erupts, forming lava that flows downhill quite easily. Effusive eruptions build up gently-sloping Shield Volcanoes like Hawaii.
What are the 5 volcanoes in Hawaii?
Hawaiian Volcano Observatory
- Kīlauea.
- Mauna Loa.
- Hualālai.
- Mauna Kea.
- Lō’ihi.
- Haleakalā
Where are composite volcanoes located?
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.
What are the 3 characteristics of a 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.
Which lava has the highest viscosity?
rhyolitic magma
The magma that has the highest viscosity is rhyolitic magma.
What type of volcano has low viscosity?
Shield volcanoes
Shield volcanoes 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.
How does a stratovolcano erupt?
Eruption. The eruption of a stratovolcano begins when a central vent emits pyroclastic material and lava. This will usually happen as an explosion of gases, unlike a Hawaiian volcano, in which lavas seem to flow like thick water. When an explosion occurs, rock and debris are ejected into the air.
How are stratovolcanoes formed?
A stratovolcano is a tall volcano shaped like a cone, formed by various layers of materials such as volcanic ash, hardened lava, pumice, and tephra. Stratovolcanoes are steep and have periodic explosive and effusive eruptions, although some have calderas, which are collapsed craters.
What are the physical characteristics of a volcano?
A volcano is generally a conical shaped hill or mountain built by accumulations of lava flows, tephra, and volcanic ash. About 95% of active volcanoes occur at the plate subduction zones and at the mid-oceanic ridges (Figure 10n-1).