Volcanoes Flashcards
What are the features of shield volcanoes
Gentle slopes and wide base
Frequent eruptions of basic lava
Lava flows at high speeds and long distances
Non violent eruptions
Non viscous lava because of basaltic compositions
Found at constructive boundaries
What are the features of composite volcanoes
Steep sided with a cone shape
High with narrow base
Explosive eruptions of lava and ash
Layers of alternating ash and lava
Viscous lava builds in layers and doesn’t flow far
Found at destructive plate boundaries
Parasitic volcanoes formed when main vent is blocked
What does more silica mean in lava
More silica = more viscous
What does more silica mean in lava
More silica = more viscous
Why does high viscosity cause explosive reactions
Gas in magma can’t escape easily causing violent eruptions
What is the VEI
The volcanic explosivity index is a scale used to measure how intense a volcanic eruption is
What are three way we can monitor volcanoes
Geological observations
Seismic activity
Gas emmissions
How do we monitor volcanoes using geological observations
Slope angler - a tiltmete4 is put onto a slope on the volcanoes side- when magma fills magma chamber the slope of the volcanoe changes-changes shown on tiltmeter
Edm- used to measure horizontal movements - before eruption the distance will change and be recorded
How can we monitor volcanoes using seismic activity
Earthquakes and tremors occur as a volcano prepares tk erupt- increase in seismic activity =more likely a volcanoes will erupt
Because many volcanoes are along plate boundaries it is often difficult to tell whether seismic activity is because of an eruption of not
How can we use gas emissions to monitor volcanoes
As magma nears the surface gases escape
Sulphur dioxide is one of the main gases - increase sulfur means increasing amounts of magma near the surface
Gas emissions might drop before an eruption because of sealing of gas passages by hard magma
This leads to increased pressure and increased chance of explosive eruption
What is “mudflows” , why are they harmful and hiw are they caused
A most flowing movement of debris that has been liquefied travel at 3-5m/s
Muflows can happen after an eruption when new , loose sediment is formed in the steep slopes of a volcano and mixed with heavy rainfall
Can carry cars , boulders and trees causing damage to water gas and electrical infrastructure
What is nuees ardentes, how is it formed and why is it harmful
A fast moving cloud of hot gas and ash
They form during explosive eruptions when columns of erupted material collapse or when volcanic rock collapses in non volcanic eruptions
Nuees ardentes can travel 50mph and range from 204-702 degrees
What is acid rain , how is it formed and why is it harmful
Acid rain is rain that is unusually acidic and ranges from ph 4-5
Sulfur dioxide gas forms acid rain and air pollution downwind from a volcano
Corrosion of steel structures(bridges)
Destroys aquatic life forms and insects
Weathering of ston buildings
Negatively affects freshwater and soils
What are lava flows , how are they formed and why are they harmful
A stream of molten rock that pours out of a volcano during an eruption
A volcano erupts and the rock is so hot it remains molten and flows down the volcano
They typically move quite slow and are known to destroy buildings than cause any threat to human life
What are gas emissions after a volcano , why do they occur and how are they harmful
After an eruption large amounts of gases are release (c02 and sulphur dioxide are a couple)
Respirory issues - death
Also have a significant effect on global climate - worsen global warming
