Science: Volcanoes Flashcards
What is a volcano?
A volcano is a vent in Earth’s surface through which molten rock flows.
Where do volcanoes form?
Volcanoes form along divergent and convergent boundaries, and hot spots like the Hawaiian Islands.
What are the three types of volcanoes?
Shield volcanoes
Composite volacnoes
Cinder cone volcanoes
Shield volcanoes
They form along divergent boundaries and oceanic hot spots. They are large with gentle slopes of basaltic lavas.
Composite volcanoes
They form along convergent boundaries from explosive eruptions of andesitic and rhyolitic lava and ash. They are large, steep sided volcanoes.
Cinder Cone volcanoes
They are made from midly explosive eruptions. They are small, steep sided volcanoes that erupt gas-rich, basaltic lavas. Some are classified as super volcanoes.
What is volcanic ash?
Volcanic ash are tiny particles of pulverized volcanic rock and glass high into the atmosphere.
Magma Chemistry (silica & viscocity)
Magma with low silica has low viscocity (it flows easily). It flows as as fluid as lava. The lava cools, crystallizes,and forms volcanic rock basalt. Magma with high silica has high viscocity. It flows like sticky toothpaste, and forms when rocks high in silica content melts.
Dissolved gases
all magmas contain dissolved gases, mainly water vapor and small amoutns of carbon and sulfur dioxide.
Relation of magma with pressure
As magma moves towards the surface, pressure from the weight of the rock above decreases. As the pressure decreases, the gases can no longer stay dissolved in the magma. Gases cannot easily escape escape from lava with high viscocity.
What often causes explosive eruptions?
The combination of high viscocity lava and large gas bubbles.
What are the effect of volcanic eruptions?
Lava flows, mudflows, and pyroclastic are some materials that flow out of lavas after an eruption. Some materials can enrich soil and rock with nutrients and help regulate climate, but they can also be destructive.
Lava flows
They move so slowly that they are raely deadly.
Ash fall explosive
These eruptions can spew ash high into the air, which can cause breathing problems. Large quatities can block sunlight and cooling the atmosphere.
Mudflows
The thermal energy cause by the eruptions can melt snow and ice on a volcano’s summit.
