Volcanoes: Eruptions and Impacts Here the volunteers will introduce themselves and the topic.

What are volcanoes? Does anyone know what a volcano is? A volcano is a landform (usually a mountain) where liquid rock erupts through the surface of the planet. The name "volcano" has its origin from the name of Vulcan, a god of fire in Roman mythology. https://www.youtube.com/watch?v=TVR_XfeDCjk

Where do you find volcanoes? The Earth’s crust is cracked into tectonic plates. These plates ‘float’ on the mantle. Sometimes these plates collide and sometimes they diverge. The earth’s crust is split into tectonic plates, which move around on the mantle due to circulation currents within. These plates can pull apart, collide and move past each other. Plates are either oceanic or continental. Can anyone name any of the major tectonic plates? Major: Pacific Plate North American Plate Eurasian Plate African Plate Antarctic Plate Indo-Australian Plate South American

https://www.youtube.com/watch?v=KdvGI1r_OTU

The different directions that these plates move due to differences in heat inside the mantle called convection currents, and this movement creates plate boundaries.

Constructive Plate Boundaries At constructive plate boundaries new crust is created. The plates are pulling apart from each other allowing magma to erupt through a volcanic vent. This boundary is usually under the ocean however in some places it can be seen on land, does anyone know an example of this? ICELAND – This plate boundary can be seen on land as Iceland is situated on the mid-atlantic ridge (a large boundary where the plates at the bottom of the atlantic ocean are moving apart)

Destructive Plate Boundaries At destructive plate boundaries the plates are converging, if an oceanic crust converges with a continental crust, because the oceanic crust is heavier and denser than the continental crust it is forced down into the mantle. Because it is heavier, the oceanic plate ‘goes under’ the lighter continental plate. This area is called the subduction zone. Here the intense heat from the mantle melts the crust. The magma then can rise. Can anyone think of an example of where a destructive plate boundary is? SOUTH AMERICA - Andes, Nazca plate subducts the south American plate ALONG COAST OF ASIA/JAPAN – where the pacific plate subducts the the Eurasian plate

Hotspot Volcanoes Hotspot Volcanoes form in the middle of plates, a hot mantle plume forces its way through the crust and slowly builds a volcano. Hawaii is an example of a volcanic island trail. To form island trails what do you think is moving? The plate or the plume?

Parts of a volcano Main Vent Secondary vent Ash Cloud Crater Lava Layers of lava and ash Magma Chamber Get the children to fill in their own diagrams while explaining where the labels go.

Parts of a volcano Ash Cloud Crater Lava Secondary vent Layers of lava and ash Explain diagram (which is being drawn tomorrow) Main Vent Magma Chamber

Do all volcanoes erupt all the time? Volcanoes can be described as: Active- a volcano that erupts regularly Dormant- is an active volcano that is not erupting, but supposed to erupt again Extinct- has not had an eruption for at least 10,000 years and is not expected to erupt again in a comparable time scale of the future Volcanoes can be active, dormant and extinct. Can anyone think of an active volcano? Can anyone think of a dormant volcano? Can anyone think of an extinct volcano?

Active Mauna Loa - Hawaii

Dormant Vesuvius - Italy

Extinct Volcano O’Leary Peak - Arizona

Types of Volcanoes Composite volcanoes are steep-sided and cone-shaped, made up of layers of ash and lava and containing sticky lava which doesn't flow very far. Found at destructive boundaries, they often have very violent eruptions, and can cause pyroclastic flows and lahars when water mixes with volcanic ash and muds. These are very violent because it’s harder for the gas to escape these volcanoes, which causes more explosive eruptions. These volcanoes are also referred to as ‘stratovolcano’ Example of composite volcano – Mt Fuji, Japan is an active volcano which last erupted in the early 1700s

Types of Volcanoes Shield volcanoes have gently sloping sides and runny lava that covers a wide area. Gases escape very easily from shield volcanoes. This makes eruptions less violent. These volcanoes tend to be found at constructive boundaries, the lava tends to flow further than at composite volcanoes. Example of a shield volcano: Mauna Loa, Hawaii (shown in the picture), which last erupted in 1984

During an eruption… Gases and lava are expelled from the vent. As well as volcanic bombs Depending on the type of volcano the characteristic of the eruption will be different. Pyroclastic flows are common at composite cone volcanoes, they are a superheated mixture of steam and rocks that rolls down the slides of a volcano at high speed.

Impacts Positive Negative The dramatic scenery created by volcanic eruptions attracts tourists Many lives can be lost as a result of a volcanic eruption. Very fertile soil in the area surrounding the volcano which is good for agriculture Lahars The high level of heat and activity inside the Earth, close to a volcano, can provide opportunities for generating geothermal energy. Lava flows and lahars can destroy settlements and clear areas of woodland or agriculture.   Human and natural landscapes can be destroyed and changed forever. The dramatic scenery created by volcanic eruptions attracts tourists. This brings income to an area. Many lives can be lost as a result of a volcanic eruption. The lava and ash deposited during an eruption breaks down to provide valuable nutrients for the soil. This creates very fertile soil which is good for agriculture If the ash and mud from a volcanic eruption mix with rain water or melting snow, fast moving mudflows are created. These flows are called lahars. The high level of heat and activity inside the Earth, close to a volcano, can provide opportunities for generating geothermal energy. Lava flows and lahars can destroy settlements and clear areas of woodland or agriculture. Human and natural landscapes can be destroyed and changed forever.

https://www.youtube.com/watch?v=U1pGxuWyKfo

Summary Composite Cone volcanoes are steep sided and tend to have explosive eruptions Shield Volcanoes have gentle slopes and runny lava Volcanoes can destroy infrastructure and settlements, and lives can be lost Volcanoes can provide fertile soils and dramatic scenery which can bring income to the areas surrounding them.

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