Volcanoes and Igneous Rocks PDF

Volcanoes and Igneous Rocks Volcanoes  http://www.youtube.com/watch?v=Be7o6BYVOzA • Definition of Volcano • Mountain that forms when molten rock (magma) is forced to the Earth’s surface What are Igneous rocks? • Ignis = fire in Latin • So… • Igneous rocks are rocks that have formed when mol...

Volcanoes and Igneous Rocks Volcanoes  http://www.youtube.com/watch?v=Be7o6BYVOzA • Definition of Volcano • Mountain that forms when molten rock (magma) is forced to the Earth’s surface What are Igneous rocks? • Ignis = fire in Latin • So… • Igneous rocks are rocks that have formed when molten material from within the Earth cools and becomes solid. • Molten material is called Magma when it is below the ground and Lava when it is above the ground. • Magma reaches the Earth’s surface when volcanoes erupt. • When magma is solidifying, particles in the liquid may Igneous rocks Characteristics of Igneous Rocks • Hard: Because the minerals they contain are hard • Strong: Because the mineral crystals that make them are strong • Made of interlocking crystals that have grown into each other and lock together. • Igneous rocks are classified according to how they were formed and the texture and colour of the rock. Minerals • Are the building blocks of rocks • Have a (very complex) chemical formula • Examples are • Quartz • Mica • Feldspar Mineral Characteristics • Crystal structure • Lustre – how light reflects • Pigment and streak – what colour it ‘draws’ on a tile • Hardness Types of rocks: Sedimentary • Formed from weathered sediment • Transported and deposited and compacted • Course or fine grained according to speed of transporting medium • Sharp or rounded particles depending on how much they are ‘rubbed’ during transit. • Eg, Sandstone, conglomerate, shale Types of rocks: Metamorphic • Formed when any type of rock is stressed and ‘cooked’ under heat and pressure. • Causes rocks to ‘laminate’ into layers • Caused rocks to harden. • Shale becomes slate. The rock cycle • Describes how rocks do not disappear but are gradually recycled over millions of years.