N THROUGH R: •
Oolith – this is a small, round piece of calcium carbonate made through the rolling wave action of water in shallow seas.
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Oolitic limestone – this is limestone you see with small grains in it called ooliths. It is made when calcium carbonate precipitates in warm seawater near the shallow coastline.
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Oxidation – a chemical process occurring between certain metal elements and oxygen. It is what happens to make rust-colored oxides and "rust" out of surface iron deposits.
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Pahoehoe – this is the Hawaiian name for the ropy surface lava formed in a skin that folds into twisty shapes while hotter lava flows beneath it.
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Pebbles – a rock piece that is usually round and less than 10 cm in total size (but usually larger than 1 cm).
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Pele's hair -this is a form of lava that forms a fine stringy pattern as it cools rapidly so it looks like hair.
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Physical weathering – this is the type of weathering that happens from mechanical breakdown of surface rocks.
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Pillow lava – this is lava that looks like pillows formed when it comes into contact with cold seawater. It comes up from the seafloor.
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Plate tectonics – this describes the very slow motion of the major ridge plates on the earth's lithosphere.
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Playa – this is a lake you might see in a desert that is only temporary. Usually these are seen dried out unless there has been recent rainfall.
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Plucking – this is a glacial term where rock at the base of a glacier gets eroded from a combination of icing and movement.
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Porous – this is a phenomenon where sedimentary rock (mostly) has spaces that have filled in with groundwater.
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