PCC - Physical and Chemical Changes Module Overview

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Physical and Chemical Changes

physical and chemical changesImagine that the Earth was made completely of water; ignoring the gravitational effects of the sun, moon, and other planets, every point on Earth's surface would be the same distance to the center. The gravitational pull on the surface would distribute water evenly around the center; Earth would be as round and as smooth as a marble. The fact that a large portion of Earth's surface is land does not change the fact that gravity is exerting a force on it, but it does affect how and when material moves towards this ideal state of equilibrium. In other words, there are additional forces that are causing the surface of Earth to be covered in irregular landforms; this chapter explores the different forces of change and their effects on the surface of Earth.

Essential Questions:

  • How do both sudden and gradual mass wasting events create various geologic hazards?
  • What can the characteristics of sedimentary materials tell us about the energy by which they were transported and deposited?

Key Words:

  1. Aa- rough, chunky lava formed when the outer surface of fast moving lava cools quickly, forming a "skin" that is broken apart as the interior lava continues to surge forward
  2. Carbonation Reaction- a type of chemical weathering caused by the mixing of water with carbon dioxide to make carbonic acid; important in the formation of caves and sinkholes
  3. Creep- slow, downslope movement of particles that occurs on every slope covered with loose, weathered material
  4. Erratic- a piece of rock that has been eroded and transported by a glacier to a different area; it is left behind when the ice melts; providing information about the direction of ice movement and distances of transport
  5. Fault-Block Mountain- formed by the movement of large crustal blocks when forces in the Earth's crust pull it apart. Some parts of the Earth are pushed upward and others collapse down
  6. Fall- a type of mass wasting that involves vertical dropping of material through air
  7. Flow- a type of mass wasting that involves the rolling of sedimentary material along a slope
  8. Hydrolysis Reaction- the chemical breakdown of a substance when combined with water. The most common example is feldspar in granite rocks changing to clay
  9. Mass Wasting- movement in which bed rock, rock debris, or soil moves downslope in bulk, or as a mass, because of the pull of gravity
  10. Oxidation Reaction- a type of chemical weathering in which oxygen combines with other elements in rocks to form new types of rock. These new substances are usually much softer, and thus easier for other forces to break apart
  11. Pahoehoe- smooth, ropey-textured lava formed when low-viscosity, gradually flowing lava cools slowly, allowing a uniform hardening of the interior and exterior
  12. Plateau- a flat, elevated landform that rises sharply above the surrounding area on at least one side
  13. Slide- a down-slope movement of material that occurs along a distinctive surface of weakness such as a fault, joint or bedding plane. Differs from a flow due to the individual particles not moving as a single, cohesive unit
  14. Talus- rock debris accumulated by mass wasting processes, most predominantly where the climate enforces on steep rock walls or cliffs physical weathering

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