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Volcanoes & Rocks

Volcanoes & Rocks. Volcanoes. Volcanoes are formed when molten rock, or magma, from the earth’s mantle, bursts through a weakness in the earth’s crust. The eruption of a volcano is usually spectacular: The red-hot molten rock released is called lava. The Ring of Fire.

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Volcanoes & Rocks

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  1. Volcanoes & Rocks

  2. Volcanoes • Volcanoes are formed when molten rock, or magma, from the earth’s mantle, bursts through a weakness in the earth’s crust. • The eruption of a volcano is usually spectacular: The red-hot molten rock released is called lava.

  3. The Ring of Fire The Ring of Fire lies along several of the Earth’s plates in the Pacific Ocean. The presence of so many active volcanoes suggests that the ring of fire is a giant weakness in the Earth’s crust.

  4. Push, push, push… Volcanoes are caused by a process called SUBDUCTION. During this process, the oceanic crust and the continental crust push against each other. The oceanic crust is heavier, so it passes below the continental crust. Cracks in the continental crust are formed, and hot magma from the mantle is expelled out in the form of lava! http://www.youtube.com/watch?v=ANeH9W-HMPc

  5. Famous Volcano Eruptions: POMPEII http://www.youtube.com/watch?v=gmwylbF3-CA&feature=related

  6. School of Rock

  7. A little about them… For many years, geologists have used evidence found in rocks to try and establish the ago of the earth. There are many kinds of rocks, but all rocks can be classified into three basic groups.

  8. 1. Igneous Rocks Igneous rocks are formed above or below the Earth’s surface from hot, molten rock called magma which comes from inside the Earth, and has cooled down and become solid. Lava from volcanoes cools down to become igneous rocks. Igneous means ‘fire-like’.

  9. Examples of Igneous Rocks • The appearance of igneous rocks depends on two major factors: • Which substance it contains • How quickly it cools • Examples include: • Basalt – Dark coloured rock with small crystals formed when lava cools quickly. • Granite – White pink or grey with flecks of black, large crystals, often used for buildings and even gravestones. • Obsidian – Smooth, glassy rock with no visible crystals and usually black. Formed when lava cools too quickly for visible crystals to form. Granite Basalt Obsidian

  10. 2. Sedimentary Rocks Sedimentary rocks are the result of erosion. A river scouring its way through rock and soil carries tiny particles called sediment suspended in water. The particles are carried to a lake or the sea, and slowly settle to the bottom, building up layer after layer. Over millions of years, these layers become compressed by further layers of sediment. Minerals in the water cement the particles in the layers together. These rocks often contain fossils of shellfish and other creatures.

  11. 3. Metamorphic Rocks Metamorphic rocks are rocks that have changed by heat, or by heat and pressure together, into a new kind of rock. This can happen when plates of the Earth’s crust collide, in the formation of mountains. Limestone can be changed to marble in this way. ‘Metamorphic’ mean changed. Limestone – Sedimentary rock Marble – Metamorphic rock

  12. http://www.youtube.com/watch?v=SRaInMDNyE8 http://www.youtube.com/watch?v=v3yJArifULo

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