Transcript Rocks
Rocks The Rock Cycle Interactions between water, air and land can cause rocks to change from one form to another. This process is called the ROCK CYCLE. The Rock Cycle – the basics • Rocks are broken into small pieces (sediment) • Sediment gets cemented together (makes different rocks) • Rocks get subjected to a lot of heat and pressure (makes different rocks) • Magma and lava cool (makes different rocks) Types of Rocks Rocks – any naturally occuring solid mass of mineral or mineral-like material Igneous Rocks Metamorphic Rocks Sedimentary Rocks Sedimentary Rocks How They are Made 1. 2. 3. 4. Wind and water break down the earth Bits of earth settle in lakes and rivers Layers are formed and build up Pressure and time turn the layers to rock Types of Sedimentary Rocks Sandstone Limestone Gypsum Conglomerate Shale Sedimentary Rock: Formation • Weathering – breaks rock into sediments • Erosion – weathering combined with movement of rock sediment (Water, wind, ice, gravity) • Deposition – process of sediment being moved by an element of erosion to another place • Compaction – sediments are squeezed together • Cementation – dissolved minerals fill in the spaces between sediments Sedimentary Rock: Classification • Clastic – made from weathered bits of rock and grouped according to the size of sediments in the rock EX. Shale and Breccia • Chemical – made from dissolved minerals “falling” out of solution. This usually happens when water evaporates. EX. Limestone and Rock Salt Metamorphic Rocks What are They? 1. Rocks that have changed 2. They were once igneous or sedimentary 3. Pressure and heat changed the rocks Types of Metamorphic Rocks Schist Gneiss Metamorphic Rock: Formation • Occurs when temperature and pressure are high in the Earth’s surface and mantle • Contact Metamorphism – magma intrudes into existing rock, changes in the rock occur where the magma touches the existing rock • Regional Metamorphism – mountain building – large scale changes • Agents of Metamorphism – heat, pressure, reaction to water Metamorphic Rocks: Classification • Foliated – layered looking. These layers have different densities EX. Shale • Non-foliated – no layers or bands. Usually have only one mineral EX. Marble Igneous Rocks What are They? 1. Fire Rocks 2. Formed underground by trapped, cooled magma 3. Formed above ground when volcanoes erupt and magma cools Types of Igneous Rocks Granite Scoria Pumice Obsidian Classification: Igneous Rocks • Intrusive – made beneath the Earth’s surface (from magma) • Extrusive – made above the Earth’s surface (from lava) • REMEMBER – magma and lava are the same thing. Except we call magma lave when it reaches the Earth’s Surface Classification: Igneous Rocks - cont • Course-grained texture – large crystals, slow cooling • Fine-grained texture – small crystals, fast cooling • Glassy texture– little to no crystals, crazy fast cooling • Porphyritic texture – large and small crystals due to cooling that occurs over thousands of years Igneous Rock Composition • Granitic – makes up continental crust • Basaltic – makes up the ocean floor These rocks are made of different concentrations of materials like silicate. Granitic - high silicate concentration. Basaltic - low silicate concentration. These differences effect rock density. Rock density determines how plates of rock move. Important for when we talk about Plate Tectonics.