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Activity at plate boundaries-volcanos - Coggle Diagram
Activity at plate boundaries-volcanos
Volcanic activity
Most volcanic activity takes place along plate boundaries
Volcanic activity can result in:
Mid-ocean ridges and islands
Volcanic cones
Mid-ocean ridge
It is an underwater mountain range,
It is formed where two plates separate
As the plates move apart, molten magma rises from the mantle and fills the gap between the plates
When the magma meets the cold seawater, it cools and becomes solid to form a new ocean floor.
As the eruptions of magma continue in an endless cycle, the ocean floor is built up to form a long ridge of mountains.
The Mid-Atlantic Ridge
It runs north to south for the full 16,000km length of the Atlantic Ocean.
It’s so high in places that it is exposed above sea level as islands
Eg. Iceland
Iceland is one of the few places where the Mid-Atlantic Ridge is exposed above the ocean
It is only about 20 million years old, making it the youngest country on Earth
Volcanic activity plays a major part in the economy of Iceland in the following ways
Tourism
Tourism is a big economic activity in Iceland.
Tourists come to see Icelands volcanic landscape.
Some of the underground water comes to the surface as host springs and geysers.
Geysers are natural fountains of hot water and steam. These are said to have healing powers due to the minerals in the water and are natural spas.
Many tourist visit these spas, such as the Blue Lagoon.
Minerals and soils
Lava from deep within the earth contains minerals. Many of these are found in spa waters. Other minerals, such as sulfur and gypsum, were mined in the past
All soils in Iceland owe their origin to volcanic activity.
Geothermal energy
Geothermal energy is created by hot water or steam, from deep beneath Earth's surface, being converted into electricity. It works like this:
• Magma comes close to the surface and heats underground water to temperatures over 400°C.
•
The steam is used to generate electricity.
When the water reaches the surface, it turns to steam.
Geothermal energy provides almost 30% of Iceland's electricity needs. It is used to:
Heat more than 85% of homes and offices
Provide power for factories
Heat greenhouses, enabling farmers to grow flowers and vegetables all year round
Help keep the pavements free of ice in winter.
How humans interact with volcanoes
Volcanic mountains
Volcanic mountains are formed when molten magma emerges or erupts through a hole in the crust called a vent.
They are generally found where plates are pulled apart or are in collision
Because the magma is under great pressure in the mantle, many eruptions are violent.
Magma finds its way towards the surface through an opening in the crust called a vent. When the magma reaches the surface, it is known as lava. Layers of lava build up around the vent, where it cools up and hardens
As the cone-shaped mountain builds up, the magma continues to make its way upwards through a volcanic pipe. Sometimes layers of ash also help to build the cone.
The lava continues to spill out of the volcano through an opening called a crater. Other materials, such as ash, gas, steam, rocks and boiling mud, can escape during an eruption
Pacific ring of fire
More than half of the world's active volcanoes are found along the Pacific Ring of Fire.
This is a zone that encircles the Pacific Ocean, where many of Earth's plates are in collision
Impacts of Mount Saint Helens
Human impact
The force of the blast and poisonous gas killed 57 people. Some were geologists, but the majority were so-called 'disaster tourists'.
Economic impact
12 million farmed fish were killed
200 homes were destroyed or extensively damaged
300 km of highway had to be rebuilt
25 km of railways had to be replaced
Forests were destroyed up to 25 km from the volcano, as were camps for the loggers.
Environmental impact
The force of the eruption reduced the height of the mountain by 400 metres.
A new crater, almost 3 km wide, was created.
Forests were stripped from hills. Trees of 2 metres in diameter were mown down as if they were blades of grass as far as 25 km from the volcano.
The eruption melted glacial ice and snow at the summit. This water combined with ash to form mudflows that clogged shipping channels in nearby rivers.
Almost 7,000 large animals (deer, elk and bear) were killed in the blast.
Mount St Helens is a mountain peak in the Cascade Range in the USA.
It was formed by a series of volcanic eruptions over thousands of years. By 1980, it had been dormant for so long that people living in the region thought it would never again erupt.
A series of earthquakes early in 1980 indicated that the mountain was beginning to rumble again. Soon steam and small lava flows began to appear from the crater. One side of the mountain began to bulge as pressure built up. It swelled outwards by over 100 metres before a massive eruption took place. Clouds of steam, gas and ash escaped in a huge volcanic explosion.
Life cycle of a volcano
Volcanoes can be classified as
Dormant
The volcano has been quiet for hundreds of ears but may erupt again. Mount St Helens had not erupted for over 120 years when it became active again in 1980.
Extinct
The volcano has not erupted in recorded times (thousands of years).
Eg Slemish Mountain in Co. Antrim
Active
The volcano is still erupting at regular intervals,
Eg Mount St Helens, USA
