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Time and Change & Rocks and Structures

Time and Change & Rocks and Structures

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Time and Change & Rocks and Structures

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  1. Time and Change & Rocks and Structures The Earth is about 4.5 billion years old.

  2. From: Humans have been here for a VERY small part of Earth’s history. How do we know the rest?

  3. Some changes take place very quickly! From

  4. Some are much more gradual, but still dramatic!

  5. Absolute Age – The Actual time of an event in Years Relative Age – The Order that events took place.

  6. Families of Rocks IgneousSedimentaryMetamorphic Igneous – Were at one time in a hot, liquid state.

  7. Magma is molten rock that is underground Magma

  8. Molten rock on the surface of the earth is called lava.

  9. When lava is blown out of a volcano in small particles it is called volcanicash.

  10. Rocks formed from lava or ash are called volcanic rocks. Basalt Obsidian

  11. Pumice

  12. Plutonic Rock – From magma that has cooled and crystallized beneath Earth’s surface. Granite is plutonic

  13. Solidifies as Plutonic Rock

  14. When softer sedimentary rock is eroded, it will sometimes leave the harder plutonic rock formations.

  15. Sedimentary rock usually consists of rock fragments such as mud, sand or gravel that have been cemented together.

  16. Weathering – the physical or chemical breakdown of rock exposed to water, wind or ice. The particles resulting from weathering -carried by rivers to the sea floor-settle to form layers of sediment-become sedimentary rock

  17. If plant or animal remains are buried, they may be preserved as fossils.

  18. A Leaf Fossil


  20. Metamorphic rocks were once igneous or sedimentary. They have been changed by heat and pressure under the ground.

  21. Shale (sedimentary) becomes Slate (metamorphic)

  22. Geological Structures Fractures are cracks in a body of rock.-can be formed by water freezing, earthquakes etc.

  23. A fault is a fracture along which there has been movement. Faults can be caused by earthquakes.

  24. Dikes are igneous rocks formed in rock fractures when magma is squeezed upward and later cools.

  25. A dike at Shiprock New Mexico

  26. Folds occur when layers of sedimentary rock are squeezed and then buckle.

  27. Erosion Surfaces-when rock has been exposed to weathering and erosion and later reburied, the boundary is rough and uneven.

  28. Strata – means there are layers.

  29. Identify the structures in the diagrams on page 261 of the Text