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JC Geography - 1.2 Volcanic Activity
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- Junior Cert geography chapter 1 the earth 1.2 volcanic activity these are the key words that you need to know by the end
- of the chapter mark Morozov war event crater lava active volcano dormant volcano extinct volcano disaster tourists mid-atlantic
- ridge and geezer you should be able to explain all of these volcanic activity takes place mostly along plate boundaries
- volcanic activity can result in the formation of volcanic mountains mid-ocean ridges and volcanic islands
- this is a satellite image of a volcanic mountain a volcanic mountain or volcano forms when magma lives up to the surface of the
- earth through event event is a small opening in the Earth's surface from which magma explodes onto the surface
- the magma is stored underground in a large chamber called a magma reservoir the magma erupts out of the vent through an opening
- called a crater when the magma reaches the Earth's surface it is known as lava the lava cools down and hardens around
- the vent other materials such as ash are also ejected from a volcano when it erupts after repeated eruptions layers of ash and lava build up around the vent
- to form a cone-shaped mountain it's important to remember that magma is
- below the ground and lava is above the ground and it is also important to remember that volcanic ash produces fertile soil when
- it is weathered and fertile soil is very good for farming types of volcano there are three types of volcano
- active dormant and extinct after volcano erupts regularly for example Mount Etna in Italy a dormant volcano has not erupted it for some time but could erupt
- again for example mount st. Helens which were opted in 1980 after 120 years mount st. helens is going to be our case study and an extinct volcano has not erupt
- 'add in historic times for example slavish mountain and county antrim
- this is a diagram of a volcano you see we have the magma chamber is located in the mantle the magma rises up through the chamber
- through the vent and eventually comes out to the top of the crater so this is the vent all along here
- and this is the crater at the top here we have smoke and ash coming out to the crater we can see that this is the lava flow
- this entire structure is called a volcanic cone then here we can see the layers of ash
- this is the mantle and this is the crust so the magma in the mantle stored in the magma chamber and rises up through the vent
- and comes out through the crater at the very top and then it comes down over the edge in a lava flow where it eventually cools down and
- hardens and forms of volcanic cone this is a photograph of slam accountant and county antrim at and it is an extinct volcano it has
- not adopted in historic times case study mount st. helens a volcano mount st. helens is a volcanic mountain in the rocky mountains USA
- it sits on a plate boundary in the Pacific Ring of Fire the volcano was thought to be dormant for 120 years until it erupted it in
- March 1980 before it erupted some small earthquakes and lava flows occurred this was a sign that the volcano was active again then
- one side of the mountain began to swell and bulge out words it's well 200 meters due to buildup of pressure eventually a massive eruption took place which
- released ash steam and gas into the atmosphere so here is Mount st. Helens before dropped it in 1980 and
- here's a picture of Mount st. Helens after it erupted and it's clear to see that the top has literally been blown off it so we now have a massive massive
- crater in the center negative effects the height of the mountain was reduced by 400 meters due to the force of the eruption a
- large crater measuring 3 kilometers wide was created in the side of the mountain snow and ice at the top of the mountain melted and mixed wood ash to form a mud
- flow the the force of the blast wiped out 25 kilometers squared of forests and trees more than 60 people were killed and over
- 250 homes destroyed roads railways and bridges were also destroyed so here is a photo of the area after the
- volcanic eruption we can see we have a police car and a policeman and he's having to wear a mask to protect himself some positive effects the eruption
- attracted to disaster tourists to the area which brought extra revenue to the region another word for revenue is money farming benefited from the fertile soil
- that was left after the volcano erupted the soil was made fertile by the ash the release of geothermal energy created hot springs
- these are a tourist attraction and they can be used to heat homes and provide energy the natural resources of the area were
- enhanced when precious stones and minerals were formed as a result of the volcano mid-ocean ridge
- a mid-ocean ridge is a mountain range that forms under the ocean as a result of our panic at iffat II and here we have a diagram of the formation of a
- mid-ocean ridge so we see we have convection currents inside the mantle they cause the plates to move to pull apart and
- the magma rises up to the surface where it starts to seep out over the edge however it is an ocean lying on top of the plate boundary
- so what happens is it seeps very very slowly out over the crust and starts to form a small little Ridge along the ocean floor
- this process continues again and again and again and eventually the small little Ridge gets bigger and bigger and bigger and peeps's head over the ocean
- and a mid-ocean ridge is formed so in some places in mid-ocean ridge is below the sea and in some places it is above the sea and when that happens we get a
- volcanic island forming so here's an example of the American plate separating from the European plate anna
- mid-ocean ridge forming in the center and an example that we will look at is the mid-atlantic ridge so we're going to look at that in a bit more detail
- so a mid-ocean ridge forms when two plates pull apart causing a fissure or crack in the Earth's crust so Fisher forms along here
- magma travels up through the fissure onto the ocean floor where it cools and solidifies which means it hardens and the magma cools and solidifies because
- it meets the cold sea water following a series of eruptions the ocean floor is built up to form a ridge of volcanic mountains
- this is a satellite image of the mid-atlantic ridge and it can actually be seen from space so here's the atlantic ocean and this is
- the ridge that runs along it and actually see it from space so the mid-atlantic ridge is an ocean ridge that runs through the atlantic
- ocean it formed when the North American plate and the Eurasian plates pulled apart the mid-atlantic ridge is
- so high in places that it reaches the surface of the ocean forming volcanic islands such as Iceland the mid-atlantic ridge runs for
- 16,000 kilometers along the floor of the Atlantic Ocean a volcanic islands volcanic island is formed when a volcanic Mountain builds
- up on the seabed until its peak appears above the surface of the ocean so here is a diagram of a volcanic island so we have convection currents
- going on inside the mantle so the plates are moving apart and we have magma rising and eventually it comes up over the surface and forms a volcanic island
- and an example of a volcanic island is Iceland and now we're going to have a look at a case study on Iceland
- case study Iceland a volcanic island Iceland is a volcanic island of the mid-atlantic ridge Iceland is 20 million years old and is
- one of the youngest countries in the world Iceland contains a number of volcanic mountains including Heckler & crafts la
- so here is Iceland you can see that the mid-atlantic ridge is running right through it this is the Eurasian Plate pulling apart from the North American
- plate and craft la is a volcanic mountain to the north of Iceland and Hecla is a volcanic mountain to the south of iceland
- hecla is the islands most active volcano so hecla right there that is the most active volcano in iceland krafla has been erupting regularly for 30 years so
- craft flow right there has been a regularly for 30 years Iceland also has many Hot Springs known as geezers
- geezers occur when water that is heated by magma under the ground rises to the surface the world-famous stroker geezer erupts
- every five to ten minutes I have possibly pronounced that wrong Hot Springs generate geothermal energy water in Hot Springs is warmed by the
- molten magma that is near to the Earth's surface this geothermal energy is used to create hydroelectricity which heats houses and towns and cities
- such as Reykjavik Iceland capital city it is very clean City as this type of energy does not release co2 gases so co2 being carbon dioxide gases which pollute
- the atmosphere Surtsey is a volcanic island off the coast of Iceland at first appeared above the sea and 1963 it is one of the
- youngest islands in the world so here is a photograph of Surtsey which is off the coast of Iceland and is one of the youngest islands in the world here's a
- photograph of a hot spring also known as a geezer and hot springs are said to have healing powers and attract many tourists to Iceland an example is the
- Blue Lagoon geothermal spa now we're going to look at an irish volcanic landform just the Giant's
- Causeway and county antrim and this is part of the Antrim dairy Plateau the ant andheri plateau formed when magma poured out of a fissure in the Earth's crust a
- fissure is another word for a crack the lava hardened to form six-sided columns of rock the Giant's Causeway is the best known section of the plateau and is a
- major tourist attraction in Ireland it is an example of an Irish volcanic landform
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