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Science Starter 9-29 WHAT ARE THE THREE TYPES OF ROCKS? Science Starter 9-30 WHAT IS WEATHERING? Science Starter 9-29 WHAT ARE THE THREE TYPES OF ROCKS? IGNEOUS, METAMORPHIC, SEDIMENTARY Science Starter 9-30 WHAT IS WEATHERING? A PROCESS IN WHICH NATURAL FORCES BREAK DOWN ROCKS Science Starter 10-3 WHAT IS A ROCK? Rocks Rocks: - Naturally formed solid substance that usually are made up of one or more types of minerals - What do we use rocks for? - Building - Sources of metals - Artwork - Pavement - Rock collections The Rock Cycle: - The rock cycle is a set of processes that form, change, break down, and re-form rocks - Rocks do not follow this cycle in any particular order Three types of rocks: 1. Igneous: forms when molten rock cools and becomes solid 2. Sedimentary: formed when rocks and other loose material get pressed together by the weight of layers of sediment above. 3. Metamorphic: Form from heat and pressure cause older rocks to form into new types of rocks Lets go rock hunting!!! How do we tell what type it is? Igneous? Sedimentary? Metamorphic? Well, turns out its not that easy… Let’s go check out our local rocks and see what we can discover! Homework! Bring in a cool rock from home! Igneous Rocks Intrusive igneous rock: form from magma cooling within the Earth. Ex: granite, quartz Extrusive igneous rock: forms when lava cools on the Earth’s surface Ex: pumice, basalt Igneous Rocks • Large crystals form when very hot magma cools slowly • Small crystals form when magma or lava cools very quickly and doesn’t allow big crystals to form • Most igneous rocks are made of silicate minerals. • Intrusive and extrusive igneous rock formations can make long lasting landforms like intrusive rock formations, volcanoes, and islands. Sediments Sediments are materials that settle out of the air or water. Sediments form sedimentary rocks when they get buried and pressed together. Some times layers called strata build on top of each other Examples of sedimentary rocks - Sandstone - Limestone - Shell conglomerate - Coal - Gypsum, rock salt, and other rocks formed from evaporated salt water Metamorphic Rocks - Metamorphism is a process in which heat and/or pressure change existing rocks - Recrystallization occurs when chemical bonds between rock molecules break and reform under heat and/or pressure - Foliation is arrangement of minerals into wavy or parallel bands. Weathering - Weathering is the process by which natural forces break down rocks - Mechanical weathering breaks up rocks with physical forces. - Ex: Ice wedging, pressure releases, plant root growth, and abrasion (break down of rocks due to friction from water or air) Chemical Weathering •Chemical weathering occurs when chemical reactions occur with rocks. •Examples: dissolving in water, acid rain, rusting Soil Humus is decayed organic material. Humus and sediment build up soil. Soil horizons are differing layers of soil. All the soil horizons of an area are called the soil profile. How are we affecting the soil? • Desertification: expanding of deserts due to plants being destroyed • Construction and development such as roads and buildings • Mining erodes the soil and leaches possible harmful minerals into the aquifers. • Industry and farming pollute soil • Destructive farming practices (remember the Dust Bowl? Let’s care for our soil!)