DEFINITIONRock Cycle • Shows the origin of the 3 basic rock types and illustrates the different geological processes that transform one rock type into another • Is the natural process in which rocks transform from one rock type into another rock type over time, a type of natural recycling.
IGNEOUS ROCKS• Ignus – “fire”• Forms as magma cools and solidifies• Intrusive • Rocks that cool inside the earth • Plutonic (Pluto – The Roman god of the Underworld) • Ex. Granite• Extrusive • Rocks that cool on the surface of the earth • Volcanic (Vulcan – The Roman god of Fire) • Ex. Basalt
INTRUSIONS• An intrusion is liquid rock that forms under Earths surface. • Batholith • a large irregular discordant intrusion • Laccolith • concordant body with roughly flat base and convex top, usually with a feeder pipe below • Stock • a smaller irregular discordant intrusion • Sill • a relatively thin tabular concordant body intruded along bedding planes • Dike • a relatively narrow tabular discordant body, often nearly vertical
EXTRUSIONS• An extrusion is liquid rock that forms above Earths surface. • Volcanoes • A volcano is an opening, or rupture, in a planets surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface. • Lava Plateau • Lava plateaus are formed by highly fluid basaltic lava during numerous successive eruptions through numerous vents without violent explosions. • Rift Valley • A rift valley is a linear-shaped lowland between highlands or mountain ranges created by the action of a geologic rift or fault.
THE PROCESSCrystallization - As magma cools, the random movement of ionsslow; and then the ions rearrange themselves into an orderlypattern.The rate of cooling influences the size of the formingcrystals. - Slow cooling results in the formation of largecrystals - Rapid cooling results in the formation of a solidmass with small interlocking crystals.
CLASSIFYINGTexture- The overall appearance of an igneous rock is based on the size and arrangement of its interlocking crystal structure.- Phaneritic - Coarse grained. Magma solidifies under the earth’s surface as a result the rocks have a large crystalline structure. Ex. Granite.- Aphanitic - Fine grained . Magma solidifies quickly on the surface of the earth. The result is a solid mass with crystals too small to be seen by the unaided eye.
CLASSIFYING- Porphyritic - Magma already contains large crystals then is ejected and the remaining magma cools quickly. The result is in appearance of a large crystal embedded in a matrix of small crystals.- Glassy - Ions in magma does not have sufficient time to unite and create a crystalline structure.
SEDIMENTARY• “sedimentum”- settling• Sediments – unconsolidated particles created from weathering and erosion of rocks. Weathering can be mechanical of chemical in origin.• Sedimentary rocks – rocks formed from the weathering of pre-existing rocks that are transported, deposited and lithified.• Lithification – process that transforms sediments into solid sedimentary rock. • Compaction • Cementation (Calcite, Silica & Iron Oxide)
CLASSIFYING• Detrital • Materials that originate and are transported are derived from mechanical weathering.• Chemical • Soluble materials that largely come from chemical weathering that are precipitated either from organic or inorganic processes.
DETRITAL CLASTICSize Range Particle Name Texture Common Detrital Rock(mm) Name> 256 Boulder Conglomerate64 - 256 Cobble Coarse (rounded edge) Gravel4 - 64 Pebble Grained Breccia (angular edge)2-4 Granule1/16 - 2 Sand Medium Sand Sandstone1/256 – 1/16 Silt Mudstone/ Very Fine< 1/256 Clay Mud Siltstone/ Grained Shale
BIOCHEMICAL NON-CLASTICComposition Texture Rock Name Fine to coarse-grained Limestone Coarse-grained fossils & fossil fragments loosely CoquinaCalcite cemented Fine-grained shells of microorganisms, clay ChalkDolomite Textures very similar to limestone DolostoneQuartz Very fine-grained Chert/FlintGypsum Fine to coarse-grained GypsumHalite Fine to coarse-grained Rock Salt Clastic – broken or fragmented Non-clastic – not formed by mechanical breakup
FEATURES• Strata or Beds • Layers of sediments that were deposited• Ripple Marks • Nearly parallel ridges and troughs produced by moving waters• Mud Cracks • Polygonal cracks that form when mud dries and shrinks• Fossils • Traces or remains of prehistoric life
METAMORPHIC• Meta • Change• Morphosis • Form• Metamorphosis • the process that changes the size, shape, texture, or even mineral composition of pre-existing rocks due to heating and pressure.
3 AGENTS OF METAMORPHISM1. Heat • Provides energy to drive chemical reactions to recrystallize minerals2. Pressure • Rocks located at a greater depth are quite warm and behave plastically during reformation3. Chemically active fluids • Water that surrounds the crystals serves as the catylist aiding the migration of ions.
2 TYPES OF METAMORPHISM• Regional • Happens in rock when subjected to intense stress and high temperatures associated with large scale deformation • Ex. Mountain Building• Contact • Happens when rock is in contact with or near a mass of magma. • Ex. Volcanic Erruptions
CLASSIFYING• Foliated • Mineral alignment that gives rock a banded or layered appearance• Non-foliated • Minerals that form equidimentional crystals is not visibly foliated.
CLASSIFYING Low Medium High Very HighFoliated M Shale Slate Schist Gneiss ENon-foliated L T Peat Lignite* Bituminous* Anthracite I Limestone Marble N Quartz Quartzite G* Still considered as sedimentary rocks.
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