Chapter 19 Section 3

Identify the three types of rocks Explain the properties of each type of rock based on physical and chemical conditions under which the rocks were formed Describe the rock cycle and how rocks change form Explain how the relative and absolute ages of rocks are determined

Mineral Igneous rock Weathering Sedimentary rock Fossils Metamorphic rock

Rocks are composed of minerals They are naturally occurring, non-living substances that have a chemical formula There are about 3500 minerals in the Earth’s crust Only about 20 are easily found in a pure state Some rocks are composed of more than 1 mineral Minerals form crystals The top nine are found quite easily Feldspar, pyroxene, mica, dolomite, quartz, amphibole, clay, and calcite

Characteristics Rocks may be porous, granular, or smooth They may be soft or hard They may have different densities or colors There are three major types of rock Igneous, formed from molten or melted rock Sedimentary, formed from the remains of other rocks or organisms Metamorphic, formed from pressure and heating

Obsidian Igneous Rock Black, extrusive igneous rock Obsidian is often called volcanic glass due to its absent crystals and glassy appearance Major minerals include feldspar, quartz and mica

Sandstone Sedimentary Rock Red, banded sample is due to iron oxidation Sandstone is formed from beach sand-sized quartz grains that are glued together with quartz or calcite Sandstone is medium- grained and is often associated with water and oil storage

Slate Metamorphic Rock Gray rock which was originally shale Slate has a fine-grained texture and is often used as a building material Slate can be broken into sheets

The deeper the rock, the older the rock Nicolas Steno: Steno proposed several laws that are still important today: the principle of original horizontality the principle of lateral continuity and the law of superposition: Assuming no change in the position of the rock layers, The oldest rocks will be on the bottom, And the youngest rocks will be on top He became a priest

Igneous rocks are the best for radioactive dating Many elements found in rock may be “dated” K, Ar, Rb, Sr, U, Pb, C In Metamorphic and Sedimentary rocks the dating only tells you when the rock was changed, not formed

There are a variety of absolute dating methods in use, most of the commonly used ones are based on natural radioactivity. In radioactive decay an atom changes to another atom as its nucleus gives off a subatomic particle. The starting atom is called a PARENT and the new one formed is the DAUGHTER, as P changes to D The rate of daughter production is constant and unique for each element. When studying a large number of parent atoms, as is usual in nature, the rate is constant.

Igneous rocks are formed from cooling molten rock Sedimentary rocks are formed by the deposition of pieces of other rocks and the remains of living organisms Metamorphic rocks form after exposure to heat and/or pressure for an extended time Rock can be recycled, (the Rock Cycle)

The relative age of rock can be determined using the Principle of Superposition Unless the rock layers are disturbed, The layers on the bottom are oldest Radioactive dating is used to determine the absolute age of rocks

10. Volcanic fumes are great for your skin 9. Crystal, Ruby, Opal…a bunch of names for your daughter 8. If you choose your field of research well, you could get paid to be at the beach 7. Diamonds are a girl's best friend 6. Rocks rock

5. Minerals generally are very accepting and non- judgmental 4. Laugh at the people who said you'd never be a rock star 3. You can get paid to date 2. "Magma" is a neat word to say. Say it with me: "magma." See? And the number 1 reason: 1. Papa was a rollin' stone