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GR 8 Unit 2 - Earth Science (Sept. 29 -Nov. 25)

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Essential Questions

When I look at a cliff, why are there different layers of rock?
How are rocks created and destroyed? 
How do tectonic plates interact to change the Earth?


  • luster - the way a mineral reflects light.  The luster can be described as metallic, nonmetallic, dull, pearly, glassy, silky
  • hardness - a measure of how easily a mineral can be scratched.
  • streak - the color of a mineral when it is in a powdered form and can be observed by scratching a mineral sample on a streak plate.
  • cleavage - describes how a rock breaks when it breaks along smooth, flat surfaces
  • fracture - describe how a rock breaks when it breaks with uneven, rough, of jagged surfaces
  • specific gravity - the ratio of its weight compared with the weight of an equal volume of water
  • acid test - applied to a mineral to determine the identify of a mineral; if the mineral fizzes when acid is applied the mineral is calcite
  • fluorescence - the ability of a mineral to glow under ultraviolet (black) light
  • igneous rock - created when magma cools either inside of or outside of the Earth's interior
  • intrusive - have large crystals, forms beneath the surface, and cools slowly
  • extrusive - have small crystals, forms above the surface, and cools quickly
  • metamorphic rock - created when already existent rocks are changed by significant heat and pressure
  • foliated - are when mineral grains line up in parallel layers (eg. slate and gneiss)
  • non-foliated - when mineral crystals grow and rearrange, but do not form layers (eg. marble and quartzite)
  • sedimentary rock -formed when older rocks are deposited and cemented together or when minerals come out of solution
  • detrital - waste, debris, broken pieces of any kind
  • chemical sedimentary rock - created when dissolved minerals come out of a solution (e.g. limestone, salt)
  • organic sedimentary rock - made of the remains of once living organisms (e.g. coal and fossiliferous limestone
  • relative age-its age in comparison to the ages of other things
  •  absolute age-the age in years of a substance
  • geologist - a person who studies rocks and the Earth
  • index fossil - the remains of a species that lived over a relatively short period of time, were abundant, and widespread geographically allowing geologists to estimate the age of a layer of rock
  • physical weathering - breaks apart rock without changing what it's made of
  • chemical weathering - occurs when chemical reactions dissolve or change the minerals of a rock
  • soil - a mixture of weathered rock, decayed organic matter, mineral fragments, water, and air
  • soil formation - a layer of sediment and mineral fragments is produced by weathering, plants and animals add organic matter (the remains of once-living organisms), and the components mix together over a long period of time (thousands of years)
  • landform - a natural feature of the earth's surface. (e.g. plains, plateaus, and mountains)
  • deposition - occurs when agents of erosion (i.e. wind, water) lose energy and drop the sediments they are carrying
  • delta - a triangular tract of sediment deposited at the mouth of a river, typically where it diverges into several outlets
  • continental drift - how the continents have  drifted into their current places and are still moving
  • Pangaea - the large landmass, a super continent, that broke apart about 200 million years ago
  • continental crust - much thicker than oceanic crust and is made mostly of granite
  • oceanic crust - much thinner that continental crust and is made mostly of basalt
  • floor spreading - he growth of oceanic crust at the mid-ocean ridge as magma escapes through weak sections of the crust
  • plate tectonics - combines the ideas of drift and spreading, and adds that large sections of Earth’s crust float on the upper mantle and are subject to move
  • convergent - when plates move towards each other
  • divergent - when plates move away from each other
  • transform - when plates slide past each other

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