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Formation of sedimentary rocks

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  • Lithification includes which two processes?
    Melting and cooling
    Weathering and erosion
    Compaction and cementation
  • During deposition
    what happens to sediments?
    They settle when energy decreases
    They turn into crystals
    They melt into liquid
  • What is the main source of sediments?
    Pre-existing rocks
    Earth’s core
    The Sun
  • Why do sedimentary rocks often contain fossils in good condition?
    They cool rapidly
    They form quickly from lava
    They form slowly at low temperatures
  • Which process changes solid rock into sediments without moving them?
    Deposition
    Erosion
    Weathering
  • Why does cementation usually occur after compaction?
    Pressure melts sediments
    Heat fuses sediments
    Water carries minerals into spaces between sediments
  • Which condition is needed for cementation to occur?
    High temperature magma
    Presence of mineral-rich water
    Strong sunlight
  • What type of sediment forms conglomerate rock?
    Melted magma
    Fine volcanic ash
    Large rounded pebbles
  • Why are fossils rarely found in igneous rocks?
    No layers form
    Pressure is too low
    Heat destroys remains
  • Why are sedimentary rocks important to scientists?
    They record Earth’s surface history
    They form only deep underground
    They show magma movement
  • What mainly causes erosion of sediments?
    Water wind and ice
    Heat from magma
    Earth’s core movement
  • How does water help cementation?
    It breaks minerals apart
    It increases temperature
    It carries dissolved minerals
  • Which mineral commonly causes cementation?
    Iron metal
    Plastic or rubber
    Calcite or silica
  • What happens to pore spaces during compaction?
    They fill with air only
    They increase in size
    They become smaller
  • Why do sediments form layers?
    All sediments fall at once
    Layers form only underground
    Different sediments settle at different times
  • How does sediment size affect deposition?
    All sediments settle together
    Larger sediments settle first
    Smaller sediments always settle first
  • Which environment is MOST suitable for thick sedimentary rock layers?
    Volcanic vents
    Mountain cores
    River deltas and seabeds
  • Which sedimentary rock forms from compacted clay?
    Basalt
    Granite
    Shale
  • Why are older sediment layers usually found at the bottom?
    They were deposited first
    They are heavier
    They formed by heat
  • Which sequence correctly shows how sedimentary rocks are formed?
    Weathering-erosion-deposition-compaction-cementation
    Melting-cooling-solidification
    Heat-pressure-recrystallization
  • What evidence shows a rock formed from sediments?
    Glassy texture
    Visible layers and grains
    Interlocking crystals
  • Which factor does NOT affect sedimentary rock formation?
    Magnetic force
    Water movement
    Gravity
  • What increases the rate of compaction?
    Less pressure
    Lower temperature
    More layers piling on top
  • What would happen if compaction did not occur?
    Rock would melt
    Fossils would burn
    Sediments would remain loose
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