the rock cycle
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The Rock Cycle. The Rock Cycle. Igneous Rocks – cooled magma or lava Sedimentary Rocks – pieces of other rocks or from minerals dissolved in water Metamorphic Rocks – heat and pressure; not completely melted, but are re-shaped while soft. - PowerPoint PPT PresentationTRANSCRIPT
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The Rock Cycle
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The Rock Cycle• Igneous Rocks – cooled magma or lava• Sedimentary Rocks – pieces of other
rocks or from minerals dissolved in water• Metamorphic Rocks – heat and pressure;
not completely melted, but are re-shaped while soft.
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Formation of Sedimentary Rocks
I. Clastic Sedimentary RocksA. Pieces of rocks carried by an agent of erosion
1. Water2. Wind3. Ice4. Gravity
B. Sequence of rock formation1. Weathering2. Erosion/transport3. Deposition4. Burial & Lithification
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Erosion and TransportDeposition
Formation of Sedimentary Rocks
– Deposition occurs when sediments are laid down on the ground or sink to the bottoms of bodies of water.
– Sediments are deposited when transport stops. – As water or wind slows down, the largest particles
settle out first, then the next-largest, and so on, so that different-sized particles are sorted into layers.
– Since wind can move only small grains, sand dunes are commonly made of fine, well-sorted sand.
– Sediment deposits from glaciers and landslides are not sorted because both move all materials with equal ease.
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Lithification• Lithification begins as the weight of overlying
sediments forces the sediment grains closer together, causing the physical changes.
Formation of Sedimentary Rocks
• Layers of mud shrink as excess water is squeezed out.
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Lithification• Sand resists additional compaction during burial.
Formation of Sedimentary Rocks
• Grain-to-grain contacts in sand form a supporting framework that helps maintain open spaces between the grains.
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Lithification
Formation of Sedimentary Rocks
• Cementation occurs when minerals grow & cement sediment grains together into solid rock. • A new mineral, such as calcite
(CaCO3) or iron oxide (Fe2O3) grows between sediment grains as dissolved minerals precipitate out of groundwater.
• Existing mineral grains grow larger as more of the same mineral precipitates from groundwater and crystallizes around them.
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C. Features of Sedimentary Rocks1. Bedding (Layers)
a. Graded; sorted by sizeb. Unsorted; mixed sizes
Deposited by wind or ice2. Fossils-sed. rocks are the only type with fossils
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II. Chemical Sedimentary Rocks – usually
evaporites, like Halite (rock salt)
III. Organic Sedimentary Rocks – once living material. Examples:coal and limestone.
IV. Types of Metamorphism A. Hydrothermal; hot water B. Contact; touching magma C. Regional; Plate Tectonics
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III. Many metamorphic rocks are foliated. This means that they have flattened crystals.
Metamorphic Rocks
– Foliated metamorphic rocks are characterized by wavy layers and bands of minerals.
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Other Possible Paths• There is more than one path in the rock cycle.
Metamorphic Rocks
• The rocks of Earth’s crust are constantly being recycled from one type to another.
• The processes that help shape Earth’s landscapes are also part of the rock cycle.