3.1 Rock Cycle • Interactions among water, air, and land can cause rocks to change from one type to another. • The continuous processes that cause rocks to change make up the ROCK CYCLE. • Main Idea: Rocks get around and recycle!
3.1 The Rock Cycle Shows the interrelationships among the three rock types(igneous, sedimentary, and metamorphic) Magma is molten material that forms deep beneath the Earth’s surface. Lava is magma that reaches the surface. Weathering is a process in which rocks are broken down by water, air, and living things. Sediment is weathered pieces of Earth elements.
3.1 Rock Cycle • The difference between the three types of rocks (igneous, metamorphic and sedimentary) is: how the rocks are formed!!!
3.1 Rock Cycle: Rock Types Igneous Rocks • Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens. • Igneous comes from the Latin word for fire.
3.1 Rock Cycle: Rock Types Igneous Rocks • Igneous rock that cools inside the earth is called intrusive igneous rock. • Intrusive igneous rock cools slowly which gives it time for crystals to form.
3.1 Rock Cycle: Rock Types Examples of intrusive igneous rock. • Granite is the most common intrusive igneous rock.
3.1 Rock Cycle: Rock Types • Igneous rock that cools on the earth’s surface is called extrusive igneous rock. • Extrusive igneous rock cools quickly. If air bubbles are trapped in the rock during cooling, the rock can have a rough surface. • If it cools very quickly, the surface can be smooth like glass!
3.1 Rock Cycle: Rock Types Examples of Extrusive Igneous • Obsidian is volcanic glass. • Basalt is another example. • Pumice is another example.
3.1 Rock Cycle: Rock Types SedimentaryRock Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of material. Together, all these particles are called sediment.
3.1 Rock Cycle: Rock Types Sedimentary Rock The sediment is generated when these materials are weathered. Weathering is the process of breaking larger materials into smaller fragments.
3.1 Rock Cycle: Rock Types Sedimentary Rock • Gradually, the sediment accumulates in layers and over a long period of time (and with pressure) hardens into rock. Generally, sedimentary rock is fairly soft and may break apart or crumble easily. S O F T !
3.1 Rock Cycle: Rock Types Metamorphic Rock Metamorphic rocks are formed under the surface of the earth (from meta=change; morpho=form). Metamorphic rock is either igneous or sedimentary rock that (under incredible pressure and heat) gets baked. This pressure and heat rearranges the atoms of the mineral. UNDER PRESSURE!
Metamorphic Rock • So….. The chemical composition of a metamorphic rock will be the same as another rock, but the atoms will be rearranged.
Metamorphic Rock Example • Limestone is sedimentary calcium carbonate. • Marble is metamorphic calcium carbonate.
From Sedimentary to Metamorphic • Shale is sedimentary rock. • Slate is metamorphic shale.
Minerals are defined by their physical and chemical properties. There are several common characteristics that we will use in our rock lab. • Now we will explore each of these characteristics.
Physical Property: Color • Definition: The visible light that is reflected by the mineral. • Testing Method: Look at the sample and determine its color - white, black, green, clear, etc.
Physical Property: Crystal Form • Definition: Geometric shape of a crystal or mineral. • Testing Method: Examine and describe the geometric shape of the mineral - cubic, hexagonal, etc. Not commonly seen in most introductory lab samples.
Physical Property: Cleavage • Definition: Breakage of a mineral along planes of weakness in the crystal structure. • Testing Method: Examine the mineral for areas where the mineral is broken. Look for areas where the light reflects from planar surfaces. This can be easily confused with a crystal face and is the most difficult properties for students to master.
Physical Property: Hardness • Definition: Resistance to scratching or abrasion. • Testing Method: Use minerals of known hardness from the Mohs Hardness Kits. Scratch the unknown mineral with a known hardness to determine which mineral is harder. Continue doing this with harder or softer minerals from the kit until the hardness is determined (using the scale).
Physical Property: Luster • Definition: Character of the light reflected by a mineral. • Testing Method: Look at the sample to determine if the mineral is metallic in appearance (looks like a chunk of metal) or non-metallic (doesn't look like a chunk of metal).
Physical Property: Magnetism • Definition: Electromagnetic force generated by an object or electrical field. • Testing Method: Use a magnet to determine if the magnet is attracted to the sample.
Physical Property: Reaction to HCl • Definition: Chemical interaction of hydrochloric acid and calcium carbonate (CaCO3). • Testing Method: Place one small drop of HCl on a sample a watch for a reaction - effervesces (bubbles).