Volcanoes

Question 1

What are characteristics of basic lava and where it is found?

Answer 1

Found at divergent plate boundaries
-Low viscosity
-Gases escape easily
-Low silica content
-Gentle eruptions
-Cools and harden slowly

Question 2

What are characteristics of acidic lava and where it is found?

Answer 2

Found at convergent plate boundaries
-High viscosity
-strato volcanoes
- Cool and harden fast
-Gases are trapped
-High silica content

Question 3

What gases are released during an eruption?

Answer 3

Sulphur dioxide
Carbon dioxide
Chlorine
Carbon monoxide
Hydrogen

Question 4

What is tephra?

Answer 4

It is a mix of ash, rock fragments and dust emitted by a volcanic eruption

Question 5

What is a pyroclastic flow?

Answer 5

It is when volcanic material such as an ash cloud collapses and rolls down the side of the volcano at rapid speeds. they are extremely hot

Question 6

Where do hotspots form?

Answer 6

Hotspots form on areas of the earths crust where the mantle is much hotter than the surrounding magma causing the magma to burn through the plate forming a volcano on the surface. It has gentle eruptions

Question 7

What is another word for composite cones?

Answer 7

Strato volcanoes- typically form at convergent plate boundaries where there is acidic lava so has a high viscosity resulting in a steep sided volcano

Question 8

What are cinder cones?

Answer 8

Smallest type of volcano and rarely reach heights of more than 300m
Normally only erupt once-force of eruption destroys them
Most common volcano
Made from the materials of pyro clasts that clumps together after an explosive eruption
Usually found around larger volcanoes eg moana loa

Question 9

What are calderas?

Answer 9

Formed when composite/starto volcanoes erupt explode violently. As they erupt they release huge amounts f magma and the explosion can fracture the rock forming the roof of the magma chamber causing it to collapse forming a depression on the earth surface. Over time they fill with water or snow. Eg Mount Pinatubo

Question 10

What is a shield volcano?

Answer 10

Usually form at divergent boundaries or over hotpsots where there is a gentle eruption of basic lava. Layers of basic lava build up over time forming a gentle sloping volcanic mountain. Eg Mauna Loa

Question 11

What is a lava plateau?

Answer 11

Is is formed when large floods of basic lava are released onto the surface from fissure eruptions. The lava flows over a large area before cooling and solidifying and after repeated eruptions build up.

This happened in the Antrim Derry Plateau when the north American and Eurasian plate began to tear apart forming a large fissure which poured basic lava into a river valley. As the lava cooled and contracted in formed hexagonal columns of basalt as it split.

Question 12

Give an example of an intrusive landform

Answer 12

Batholith

Question 13

What are sills in terms of batholiths?

Answer 13

Sills are formed when lava forces its way between layers of sedimentary rock forming a horizontal layer of granite

Question 14

What are dykes in terms of batholiths?

Answer 14

Dykes are forced when magma forces it way through layers of sedimentary rock before cooling and forming a vertical column of granite

Question 15

What are laccoliths ?

Answer 15

They are formed when magma forces its way between layers of sedimentary rock and as more magma intrudes pressure increases and forces the rock to bulge upwards. Magma then cools slowly to form a dome-shaped layer of granite

Question 16

Describe the formation of a lapolith

Answer 16

A lapolith forms as magma forces its way into layers of sedimentary rock as as more magma intrudes pressure increases and the force causes the rock to bulge downwards forming a bowl shaped layer of granite

Question 17

What are the ways to predict volcanic activity?

Answer 17

-Gas emissions
-Historical records
-Ground deformation
-Seismic activity

Question 18

How can gas emissions predict volcanic activity?

Answer 18

Sensors are placed around the volcano to measure carbon dioxide levels and sundry dioxide emissions. These gases are produced when a volcano erupts so by monitoring to see any increases in emission of the gases they can indicate if a volcano is close to eruption

Question 19

How can historical records predict volcanic activity?

Answer 19

Volcanologists can look at historical records to look for patterns in when past eruptions have occurred to help predict time and size of eruption. They can also study volcanic deposits to determine size and type of material to be emitted.

This alone is not enough to predict must be backed up with other more modern technology

Question 20

How can ground deformation predict volcanic activity?

Answer 20

When a volcano is close to eruption the cone of the volcano can bulge. Equipment such as electronic distance metres and tilt meters are placed around the slope of the volcano.

EDM’s are placed on the slope and reflected are placed further up the slope which return a signal. If the lasted take a longer or shorter time to return it indicates a change in pressure inside the volcano.

Tilt meters have air bubbles in water that move if there is a change in the slope. This indicates the volcano is bulging due to increased pressure indicate a potential eruption

Question 21

How does seismic activity predict eruption?

Answer 21

Seismic activity around a volcano always increases before an eruption as magma and gases force their way upwards. Seismographs are placed within a 20km radius is the volcanic vents in specific areas in order to record vibrations of the crust indicating a volcanic eruption is highly possible