Warm-Up: Describe the texture and composition of each igneous rock. A B
Definition of A Rock A naturally occurring, solid, mixture of one or more minerals or organic matter Classified into 3 groups based on how they are formed: igneous, sedimentary, and metamorphic Texture and composition give clues as to how rocks are formed, and are used to classify and identify rocks Rocks are always changing form in a cycle called the Rock Cycle Rocks Rock!
Rock Classification Composition – the type of minerals a rock contains (ex: Limestone is 95% Calcite and 5% Aragonite) Texture – the size, shape and arrangement of the minerals that make up a rock. Can be fine, medium, or coarse.
The Rock Cycle The main idea of the rock cycle is that rocks are continually changing from one type to another and back again The elements that make up a rock are never created or destroyed - instead, they are constantly being recycled.
Igneous Rock Form when magma cools and hardens. Sometimes look shiny and glasslike if lava cools quickly Sometimes have tiny holes and spaces if gas is trapped in the rock as it cools Two examples are: Basalt and Obsidian
Igneous Rocks Extrusive rocks- formed by cooling lava Texture Can Be: glassy porous fine-grained Intrusive rocks- formed by cooling magma Texture Is Always: coarse-grained
Sedimentary Rock Formed from particles called sediments Fairly soft and break easily Contain sand, pebbles, stones, and is the only rock to contain fossils Examples are: Conglomerate and Limestone Form at or near Earth’s surface Most have layers or strata
Sedimentary Rocks Formed by: Weathering (breaking down of rock) Erosion (movement of sediments) Deposition (collection of sediments) Compaction & Cementation (sediments bonding together)
Two Types of Weathering 1. Mechanical Weathering Root Action Frost Action Moss
Types of Weathering 2. Chemical Weathering: Oxidation (rust) – Oxygen in air reacts with metals in rocks Acidic rain water
Chemical Sedimentary Rocks… Limestone Gypsum rock Geode
Sedimentary rocks according to texture: Coarse-grained Conglomerate Shale Sandstone Fine-grained Medium-grained
Metamorphic Rock Formed under the surface of the Earth due to extreme heat and pressure Have ribbon-like layers and may have shiny crystals formed by minerals cooling slowly over time Two examples are: Gneiss and Marble
Metamorphic Rocks Formed by tremendous heat & pressure, and chemical reactions inside the crust. Formed from all three rock types.