Science M1 Q4

• Igneous rocks


  Solid and crystalline rocks formed from molten hot rocks (magma)
• Igneous rocks


  • Formed from molten magma at high temperature and pressure deep underground
  • Can be intrusive (plutonic) or extrusive (volcanic)
• Intrusive igneous rocks


  • Granite
  • Diorite
  • Gabbro

  
• Extrusive igneous rocks


  • Rhyolite
  • Basalt
  • Andesite

  
• Sedimentary rocks


  Rocks formed from the accumulation and consolidation of sediments
• Sedimentary rocks


  • About 3/4 of rocks on Earth's surface
  • Can be formed from chemical or organic sediments

  
• Limestone is formed by deposits of calcite in coral reefs by corals and algae
• Coquina is a variety of limestone formed from pieces of algae, corals, and shells
• Sedimentary rocks


  About 3/4 of the rocks on Earth's surface are sedimentary. The sediments that comprise the sedimentary rocks may either be chemical or organic. These contain crystals and fossils.

  
• Chemical sediments


  Chemical sediments are formed when the chemicals that were dissolved in water precipitate or are left by evaporating water.
• Limestone


  • Formed by deposits of calcite in coral reefs by corals and algae. Calcite is the crystalline form of calcium carbonate.
• Coquina


  • A variety of limestone formed from pieces of algae, corals, and shells.
• Organic sediments


  Organic sediments are made up of remains of living things such as skeletons, shells, and plants.
• Coal


  Formed when plant remains like moss, leaves, twigs, roots, and tree trunks are pressed together. Over time, coal becomes black and rich in carbon. It burns easily. Since it is formed from ancient remains of plants, it is called fossil fuel.
• Sedimentary rocks


  • They contain crystals and fossils. Geologists study sedimentary rocks because of the fossils embedded in them.
• Fossils


  • Bone or shell covered by sediment before it decays. The original bone or shell is not changed but is preserved by the calcite or silica. Sometimes, the fossil disappears but leaves a mold. The mold is filled by calcite or silica and leaves a cast of the original fossil. Footprints, trails, and burrows preserved on rocks are also fossils.
• Metamorphic rocks


  Rocks that have been changed in some way. They start either as igneous or sedimentary rocks. High temperature and pressure change the rocks into new forms.
• Metamorphic rocks


  • Usually much harder and smoother than the original igneous or sedimentary rocks.

  
• Metamorphic rocks


  • Marbles (formerly sedimentary rocks made of clay), quartzite (from sandstone), slate (from shale and clay), schist (from shale), gneiss (light and dark mineral-layered rock resembling granite or diorite)

  
• Rock cycle


  Igneous and metamorphic rocks break into pieces by erosion. The eroded rock materials are transported into bodies of water by wind or rain. These materials settle and form sediments. These sediments are cemented by mud, silt, clay, and silica. They become sedimentary rocks. Sedimentary and metamorphic rocks deposited deep beneath the earth's surface melt due to extreme heat when they get near or reach the magma chambers. Then these rocks become magma. They form igneous rocks when they cool and harden. Igneous and sedimentary rocks are also buried under the crust and transformed by extreme heat and pressure to become metamorphic rocks.
• Rocks are very important in constructing houses and buildings, roads, bridges, and other structures. Without rocks, the crust of the earth would be unstable.
• Agents of weathering


  Water, wind, temperature, plants, animals, and people cause rocks to break into pieces
• Water


  Can break rocks in different ways - strong waves hitting rocks, water seeping into cracks and expanding when freezing, etc.
• Wind


  Can break down rocks through abrasion, carrying sand and other particles that scrape against rock surfaces
• Agents of weathering


  • Water
  • Wind
  • Temperature
  • Plants
  • Animals
  • People
• Mechanical weathering


  Rocks broken physically without changing composition
• Chemical weathering


  Change in rock composition allows them to break down
• Water


  • Can break rocks in different ways: strong waves, seeping into cracks, freezing and expanding
• Wind


  • Carries sand and small rocks that crash on rock surfaces, causing abrasion and wearing away of rock surfaces
• Temperature changes


  • Affect water in cracks and joints, causing freezing and expansion that breaks rocks (frost wedging)
• Plants


  • Lichens, ferns, mosses can grow on rocks and cause gradual breakage
  • Tree roots can break cemented ground
• Animals


  • Burrowing animals can cause rocks to break into pieces
• Humans


  • Use bulldozers, jackhammers, explosives to break rocks for construction, mining, etc.
• Industrialization


  Causes air pollution and acid rain that eats away at statues, buildings, roads, and bridges
• Oxidation of minerals in rocks


  Changes the physical appearance and chemical properties of rocks
• Soil


  Layer of rock and mineral fragments produced by weathering, combined with organic matter from plants and animals
• Types of soil


  • Loam
  • Clay
  • Sand
• Soil can take thousands of years to form and varies in thickness depending on climate, slope, rock type, vegetation, and weathering time