The Lithosphere What are the different types of rock? How does the rock cycle affect different phenomena in our world?
The Lithosphere • The lithosphere is the rigid structure that makes up the Earth’s crust and part of the upper mantle. • It includes mountains, plains, volcanoes, etc. • It ranges in depth from 70 km (below the oceans) to 150 km (beneath the continents)
The Lithosphere • Very essential to life: • Enables plants to have roots • Provides plants with important minerals • Habitats for animals • Contains the natural resources we need • Provides the materials we need to build with
Rock or Mineral? • Rock: a heterogeneous blend of variously sized grains of different kinds • Mineral: a pure, natural, inorganic (non-living) substance. • Minerals are the building blocks of rocks.
Granite is a rock made of: The transparent crystals are quartz The grey pieces are mica The shiny grains are feldspar The dark spots are hornblende Four minerals = one rock!
Minerals • Minerals are inorganic substances which exist naturally in the Earth’s lithosphere. • Minerals have a distinct chemical composition:
Minerals can be made up of: • single elements (gold: Au, lead: Pb) • several elements bonded together (sodium chloride: NaCl, copper sulphate: CuSO4)
Mineral Classification • Minerals are classified based on their properties, which all minerals demonstrate: • Colour • Transparency • Hardness • Streak
Colour • Many minerals have a characteristic colour, caused by either the chemical composition of the mineral (idiochromatic) or by impurities in the sample (allochromatic). Rhodochrosite is red Azurite is blue
Clarity • Clarity is the property by which a substance allows light to pass through it. • Some let light pass straight through: transparent • Others let light through, but its impossible to distinguish the object through them: translucent • Others let no rays through at all: opaque
Hardness • Hardness depends on the strength of the atomic bonds: how hard the mineral is… • The Mohs scale assigns a value from 1 to 10 to indicate the hardness: 1 is soft, 10 is hard. • A mineral will scratch all softer minerals: a mineral with hardness 4 will scratch minerals of hardness 1, 2 and 3.
Streak • When a mineral is rubbed on a porcelain surface, it leaves a powder trace. This powder may be different from the colour of the mineral.
Minerals Rocks • Minerals are combined together in various quantities to form rocks. • A rock is a heterogeneous solids composed of many minerals. • Rocks fall into three categories, depending on how they form: • Igneous • Sedimentary • Metamorphic
Types of rocks • 1) Igneous Rock • Igneous rock results from the cooling and solidification of magma. Granite Basalt Gabbro
2) Sedimentary Rock • When igneous rocks break apart these fragments (called sediment) are then carried and polished by wind and water. • They are then deposited in layers at the bottom of oceans and lakes. • Over time, these layers are compacted and cemented together to form sedimentary rock.
Sedimentary rock can contain fossils, which are the remains of plant or animal life. • Over time, the soft parts of animals are replaced by minerals, which causes the rock to retain the form of the animal. • Sometimes, we can find intact bones or teeth! A cockroach fossil in sandstone
3) Metamorphic Rock • When igneous and sedimentary rocks are pressed really hard or heated, the minerals are rearranged. They settle in bands or sheets, or change their texture. • This process creates metamorphic rock.
Gneiss has light and dark bands Mica schist has rigid bands
Crystals or bands? Gneiss has colored bands Granite has crystals