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21.3 Rocks and the Rock Cycle  Rocks are classified into three major groups based on how they formed  Igneous Rocks Can be divided into two categories.

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Presentation on theme: "21.3 Rocks and the Rock Cycle  Rocks are classified into three major groups based on how they formed  Igneous Rocks Can be divided into two categories."— Presentation transcript:

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2 21.3 Rocks and the Rock Cycle  Rocks are classified into three major groups based on how they formed  Igneous Rocks Can be divided into two categories based on where they form

3 A. Intrusive Rocks – igneous rocks that form underground from magma – Cool slowly allowing crystals to grow large giving it a coarse-grain texture

4 B. Extrusive Rocks – igneous rocks that form at the surface from lava – Cool quickly resulting in the crystals to be small giving it a fine grain texture

5 Igneous Rock Textures 

6  II. Sedimentary Rock – rock that forms over time as sediment is squeezed and cemented together – Sediment – small, solid pieces of material that comes from rocks or living organisms Sediment is deposited in layers by running water or wind Sediment is cemented together by pressure from overlying layers  Three Main Groups of Sedimentary Rocks:  1. Clastic  2. Chemical  3. Organic

7 1.Clastic Rock – sedimentary rocks that form from the broken fragments of other rocks – Clastic Rocks are classified based on the size of their fragments – Example: Conglomerate – rock fragments that consist of gravel and pebbles

8  Some clastic rocks are made of smaller particles (sandstone)

9 2. Chemical Rocks – rocks that form when minerals precipitate out of solution – Example: when ocean water evaporates (halite)

10 3.Organic Rocks– rocks that form as a result of organic processes Shells of marine animals like corals, clams, mussels sink to the ocean floor when they die. – Example: Limestone and calcite (chalk)

11  III. Metamorphic Rocks – rock that have been changed by temperature, pressure, or chemical reactions. – Most metamorphic rocks form under high temperatures and pressures deep underground. (slate and schist– shown below)

12 Metamorphic Rocks  Foliation: a layering of minerals in a rock due to intense pressure squeezing the crystals together.

13 Metamorphic Rock pictures  Metamorphic Rocks like gneiss show banding of light and dark minerals.

14 Metamorphic Rocks and their Parent Rocks  Examples: – Slate: parent is shale – Gneiss: parent is granite/schist – Quartzite: parent is sandstone – Marble: parent is limestone

15 IV. Rock Cycle  Rock Cycle – series of processes in which rocks continuously change from one type to another.


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