Where?
1) At Destructive plate margins the oceanic plate goes under the continental plate because its more dense (this also creates an ocean trench)
- The oceanic plate moves down into the mantle, where it is melted and destroyed
- A pool of magma forms
- The magma rises through cracks in the crust called vents
- The magma erupts onto the surface (where its called lava) forming a volcano
2) At Constructive margins the magma rises up into the gap created by the plates moving apart, forming a volcano
3) Some volcanoes also form over parts of the mantle that are really hot (called hotspots) e.g. in Hawaii
1) At Destructive plate margins the oceanic plate goes under the continental plate because its more dense (this also creates an ocean trench)
- The oceanic plate moves down into the mantle, where it is melted and destroyed
- A pool of magma forms
- The magma rises through cracks in the crust called vents
- The magma erupts onto the surface (where its called lava) forming a volcano
2) At Constructive margins the magma rises up into the gap created by the plates moving apart, forming a volcano
3) Some volcanoes also form over parts of the mantle that are really hot (called hotspots) e.g. in Hawaii
Intrusive and Extrusive:
1) The high pressure inside the earth keeps rocks in some parts of the mantle semi-molten
2) when the pressure is released, e.g. at constructive boundaries, the rocks become molten. The hot molten rock is called magma
3) because magma is less dense than rock around it, it rises up towards the earths surface
4) most magma doesn't reach the surface, but some does - the type of volcanic activity depends on where the magma ends up.
Intrusive:
This takes place BENEATH the surface. It includes the formation of large magma chambers and magma being forced into the crust (through cracks in the rock)
Extrusive:
This takes place ON the earths surface. The major form of this activity is volcanic eruptions of lava or other material. Minor types of extrusive volcanic activity include hot springs, geysers and boiling mud pools.
1) The high pressure inside the earth keeps rocks in some parts of the mantle semi-molten
2) when the pressure is released, e.g. at constructive boundaries, the rocks become molten. The hot molten rock is called magma
3) because magma is less dense than rock around it, it rises up towards the earths surface
4) most magma doesn't reach the surface, but some does - the type of volcanic activity depends on where the magma ends up.
Intrusive:
This takes place BENEATH the surface. It includes the formation of large magma chambers and magma being forced into the crust (through cracks in the rock)
Extrusive:
This takes place ON the earths surface. The major form of this activity is volcanic eruptions of lava or other material. Minor types of extrusive volcanic activity include hot springs, geysers and boiling mud pools.
Intrusive volcanic activity forms Dykes, Sills and Batholiths.
1) When large chambers of magma cool underground they form domes of igneous rock called Batholiths.
2) Where the magma has flowed into gaps in the surrounding rock and cooled it forms vertical dykes (across the layers of rock) and horizontal sills (between the layers of the rock)
3) Cracks may form as the magma cools- these are called cooling cracks. In a sill they're vertical, and in a dyke they're horizontal
1) When large chambers of magma cool underground they form domes of igneous rock called Batholiths.
2) Where the magma has flowed into gaps in the surrounding rock and cooled it forms vertical dykes (across the layers of rock) and horizontal sills (between the layers of the rock)
3) Cracks may form as the magma cools- these are called cooling cracks. In a sill they're vertical, and in a dyke they're horizontal
Lava eruptions are form of extrusive activity
1) There are three main types of lava
- Basaltic lava is made at constructive plate margins
- Andesitic lava is made at destructive plate margins
- Rhyolitic lava is made up at destructive plate margins
2) The different types of lava have different chemical compositions- and its the chemical composition that controls the viscosity (thickness) and temperature of the lava
3) Basaltic lava has a low viscosity so it flows easily and gas can escape from it easily. As a result, eruptions of basaltic lava aren't violent. Basaltic lavas usually erupt frequently and for long periods of time.
4) Andeitic and Rhyolitic lavas have high viscosity than basaltic lava. They flow less easily, and often form blocakages in volcanic vents. Also volcanic gases cant escape easily from viscous lava. Pressure builds up because of the lava blocakages and trapped gases, until the blockages are cleared by a violent eruption. Andesitic and rhyolitic lavas usually erupt intermittently ( every once in a while) and the eruptions are short lived.
Look at the image below which looks at the properties of lava eruptions.
1) There are three main types of lava
- Basaltic lava is made at constructive plate margins
- Andesitic lava is made at destructive plate margins
- Rhyolitic lava is made up at destructive plate margins
2) The different types of lava have different chemical compositions- and its the chemical composition that controls the viscosity (thickness) and temperature of the lava
3) Basaltic lava has a low viscosity so it flows easily and gas can escape from it easily. As a result, eruptions of basaltic lava aren't violent. Basaltic lavas usually erupt frequently and for long periods of time.
4) Andeitic and Rhyolitic lavas have high viscosity than basaltic lava. They flow less easily, and often form blocakages in volcanic vents. Also volcanic gases cant escape easily from viscous lava. Pressure builds up because of the lava blocakages and trapped gases, until the blockages are cleared by a violent eruption. Andesitic and rhyolitic lavas usually erupt intermittently ( every once in a while) and the eruptions are short lived.
Look at the image below which looks at the properties of lava eruptions.
Different Types of Volcanoes:
Hot Springs:
1) Springs are places where groundwater emerges at the surface 2) if the groundwater source of a spring flows close to an area of recent intrusive volcanic activity, the water is heated and the spring becomes a hot spring 3) The temperature of hot springs varies from around 20°C to over 90°C 4) Hot spring water often has a high mineral content because hot water can hold a lot of dissolved solids 5) Hot springs are found all over the world and are often popular with tourists e.g. the springs in Rio Hondo (Argentina) and North Island (New Zealand). Geysers: 1) Geysers are a type of hot spring where hot water and steam are ejected from the surface in a fountain. They form in areas of intense volcanic activity. This is what happens: - Ground water is heated to above boiling point by magma deep in the crust. The hot water then becomes pressurised and forces its way to the surface along cracks in the rocks. Finally the hot water and steam spray out from a vent. 2) Geysers erupt periodically. This is because they only erupt when the pressure has built up enough to force the water out of the ground 3) Examples of geysers are Strokkur (Iceland) and Old Faithful in Yellowstone National Park (USA) Mud Pools:
1) A boiling mud pool is another type of hot spring 2) They form in areas with very fine-grained soil (e.g soil rich in clay or volcanic ash) - the hot sping water mixes with the soil to create a hot muddy pool 3) the pools sometimes contain brightly-coloured mud because of minerals deposited by the hot water. E.g. iron and sulphur-rich minerals can create purple, orange and yellow colours 4) boiling mud pools can be found all over the world e.g. Yellowstone National Park (USA) |