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The exterior of the Empire State Building in NYC is
made of limestone, marble, granite, and metal.
Sedimentary &
Metamorphic Rocks
SEDIMENTARY ROCKS
• Rocks are formed by the compaction and cementing layers of sediments.
• Sediments are materials such as rock fragments, plant and animal remains, and minerals that settle to the lake or ocean floor.
Formation
• Sediments – small pieces of rock that are moved and deposited by water, wind, glaciers and gravity.
• When sediments become “glued” together, they form sedimentary rock.
• Sediments produced by weathering and erosion form sedimentary rocks through the process of lithification.
• Weathering produces rock and mineral fragments.
• Erosion removes and transports sediment.
• Lithification describes the physical and chemical processes that transform sediments into sedimentary rocks.
• Lithify means to turn to stone.
Compaction and Cementation
• Lithification begins with compaction—the weight of overlying sediments forces the sediment grains closer together.
• Cementation occurs when mineral growth glues the sediment grains together into solid rock.
Sedimentary Layers
• Bedding – the way sediment settles out of water and wind– Graded bedding: bedding in which the particle
sizes become heavy and coarse toward the bottom
– Cross bedding: formed as inclined layers of sediment deposited across a horizontal surface
Graded bedding
Cross-bedding
Classification
• Sedimentary rocks are classified by their mode of formation.– Clastic rocks– Chemical rocks– Biochemical rocks
Clastic Rocks
• Formed from the abundant deposits of loose sediments that accumulate on Earth’s surface.
• Clastic means broken.• Three types:– Coarse, medium, fine-grained
Coarse-grained rocks
Fine-grained rocks
Chemical Rocks
• The water in seas, lakes, swamps and underground reservoirs often contains dissolved minerals along the floor.
• These sediments form when these minerals precipitate or fall out of solution.
Rock Salt Flats
http://www.speedace.info/bonneville_salt_flats.htm
Biochemical Rocks
• Forms from sediments consisting of the remains of plants and animals.
• This quarry was once covered by water. Shelled organisms left behind fossils in the limestone sediment.
CoquinaFossiliferous limestoneMudstone
Sedimentary Features
• Stratification – a change in the type of sediment being laid down resulting in the formation of a new layer
• Fossils – the remains or impression of any plant or animal preserved in rock.
• Geodes – limestone that contains spheres of silica rock made entirely of quartz crystals.
METAMORPHIC ROCKS
• Rocks are formed by the effect of heat and pressure on other rocks.
• These rocks are exposed to the movements of Earth causing changes that give them new characteristics.
Textures
• Foliated – minerals are squeezed under high pressure and arranged in wavy layers or bands
• Nonfoliated – composed mainly of minerals that form blocky crystal shapes
Types of Metamorphism
• Regional metamorphism – high temperature and pressure affect large regions of Earth’s crust
• Contact metamorphism – when molten material comes in contact with solid rock
The ROCK Cycle
• Repeated series of events by which rock gradually and continually changes from one type to another