Rock Composition and Types

How could you tell how many different types of rocks are in the photo How could you tell how many different types of rocks are in the photo? What characteristics would you look for?

What are Rocks? Rocks are: naturally formed non-living Earth material Rocks are made of collections of mineral grains and/or remains of living things held together in a firm solid mass.

How is a Rock Different from a Mineral? Rocks are made of minerals mineral grains can be microscopic to larger than your finger

Identifying Rocks Rocks are identified by: 1.Composistion: minerals they contain- each type has some unique minerals 2.Texture: grain size is an important characteristic in all three types

Sample Materials Texture Formation Rock Type Left Rock plagioclase, hornblende, pyroxene crystals visible to naked eye magma cooled slowly diorite Right Rock one type of crystal visible, rest microscopic magma erupted and cooled quickly andesite

Three Types of Rocks Igneous Sedimentary Metamorphic

Igneous rocks All igneous rocks are the result of cooled magma or lava! Where the rock cools determines its appearance. Intrusive- cooled inside Earth’s crust Extrusive- cooled outside Earth’s crust

Igneous Rock Characteristics -spots or speckles -heavy or light -holes or solid -Colorful -smooth and glassy or rough and gritty

Why does it look like that composition of the minerals in the magma or lava how fast the magma or lava cools slower cooling = larger crystals faster cooling = smaller crystals

Igneous Rock Characteristics Intrusive= Slow cooling Form inside crust Coarse texture Larger, visible crystals Heavier No holes Light or dark colored depending on silica content Extrusive= Rapid cooling Form outside crust Fine texture Small or no crystals Very light May have holes Light or dark colored depending on silica content (high silica is lighter)

Sedimentary Rocks Formed by weathered sediments and dissolved minerals deposited into an area over time Compacted into layers over time Water can help cement sediments together

Sedimentary Rock Characteristics Gritty, grainy, sandy texture Made of sediment Rough or smooth depending on size of sediment Rock chuncks Fossils Layers Not shiney Earthy colors

Sedimentary Rock Formation Clastic sedimentary rocks- composed of fragments and particles derived from pre-existing rock- sandstone, conglomerate Chemical sedimentary rocks- dissolved minerals carried to lakes and seas in rivers or ground water precipitates to form chemical sediments like salt or limestone Organic sedimentary rock- made of living matter accumulated and compacted over time- coal, coquina

Transport & Deposition Sediments are transported by water, wind, ice or gravity Sediments will settle out of water when water slows. Sedimentary rocks form in layers with the youngest on the top

Sedimentary Rocks Reflect their Environment Beaches & deserts deposit sand Sediments from the bottoms of ponds, lakes, marshes, & swamps usually will be smaller and well sorted. Glaciers deposit sediment without sorting.

Metamorphic Rock Characteristics -sparkly -smooth -wavy or swirly layers -colorful -heavy -hard -solid -waxy

Metamorphic Rock Formation Heat and/or pressure change an existing rock into a metamorphic rock Change can be physical, chemical, or both Foliation can occur if the rock forms layers. Metamorphic rocks are either foliated or non-foliated.

Foliation

Metamorphic Diversity Metamorphic rocks are very diverse because there are some many different parent rocks that can be metamorphosed to various degrees.