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3 types of rocks. 3 types of rocks. There are 3 types of rocks found on Earth: Igneous Sedimentary Metamorphic Knowing the differences between these 3 types of rocks allows us to learn about Earth’s past. Igneous Rocks - Formation. - PowerPoint PPT Presentation
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3 types of rocks
3 types of rocks
• There are 3 types of rocks found on Earth:– Igneous– Sedimentary– Metamorphic
• Knowing the differences between these 3 types of rocks allows us to learn about Earth’s past.
Igneous Rocks - Formation
• Igneous Rocks are formed by melting, cooling, and crystallization of other rocks.
• Igneous rocks form as a result of volcanic activity, hot spots, and melting that occurs in the mantle.
Igneous rocks
• Igneous rocks are common along plate boundaries or mantle hot spots
Igneous Rocks - Classification
• Igneous rocks are classified using their texture in the following ways:– Glassy– Aphanitic (no visible crystals)– Phaneritic (visible crystals)– Porphyritic (Some visible and
some not visible crystals)
Igneous Rocks - Texture
• Crystal size is used to classify igneous rocks.
• Crystals form as the rock cools, and the crystal size can tell us a lot about its cooling history:– The larger the crystals,
the slower it cooled.
Igneous Rocks - Texture• Glassy igneous rocks
have no crystal structure, and probably formed by very rapid cooling (such as on the surface of a lava, or when a lava enters the water.)
Igneous Rocks - Texture
• Aphanitic rocks have no visible crystals, and probably formed by fast cooling above ground.
Igneous Rocks - Texture
• Phaneritic rocks have visible crystals, and probably formed by slow cooling below ground.
Igneous Rocks - Texture
• Porphyritic rocks have both visible and nonvisible crystals, and probably formed by two different cooling events.
Igneous Rocks - Classification
• Dark igneous rocks are formed from basaltic or mafic magma. (Mafic because it contains a lot of magnesium and iron).
• The magma that forms these rocks is usually very hot (around 1000°C) and viscous (about the same viscosity as ketchup.)
Igneous Rocks - Classification
• Light colored igneous rocks are formed from silicic (high silica content) or felsic magmas.
• The magmas that form these rocks is usually more cool, (lower than 850°C), and more viscous (about the viscosity of peanut butter.)
Igneous rocks - Formations• Structures and
formations seen in igneous rocks include: – Hexagonal columnar
joints– Pahoehoe lava flows– Dikes, sills, and
batholiths (plutons)– Pillow basalts– Volcanoes
Igneous Rocks - Examples
• The most common types of igneous rocks include:– Rhyolite– Andesite– Basalt– Granite– Diorite– Gabbro
Igneous rocks charted
Igneous rocks - Story
• What do you know about the history of the Earth in the place where this rock was found?
Sedimentary Rocks - Formation
• Sedimentary rocks are formed by weathering, erosion, deposition, compaction, and cementation of other rocks.
• Sedimentary rocks form in areas where water, wind, or gravity deposit sediments.
Sedimentary rocks - formation
• Sedimentary rocks are likely to form in areas such as:– Deltas– Beaches– Rivers– Glaciers– Sand dunes– Shallow seas– Deep oceans
Sedimentary rocks - Classification• Sedimentary rocks are
classified into two groups:– Clastic rocks– Chemically formed rocks
Sedimentary rocks – Classification
• Sedimentary rocks are Clastic if they are made of pieces of other rocks that have been weathered and eroded.
• Clastic rocks are grouped based on the size of grain that they are made from.
Sedimentary rocks - Classification
• Very small particles make up mudrock.
• Medium sized particles make up sandstone.
• Large particles make up conglomerates.
Sedimentary rocks - Classification
• Sedimentary rocks that form from chemical processes are called biochemical rocks (formed from living things) or Chemical precipitates (formed from lakes or shallow seas.)
Sedimentary rocks - formations
• Structures and formations seen in sedimentary rocks include:– Stratification– Cross bedding– Graded bedding– Ripple marks– Mud cracks– Fossils
Sedimentary rocks - Examples• Some of the most
common types of sedimentary rocks include:– Conglomerate– Sandstone– Shale– Limestone– Gypsum– Oolites– Chert (including black
flint and red jasper)
Sedimentary rocks - Story
• What do you know about the history of the Earth in the place where this rock was found?
Metamorphic rocks - Formation
• Metamorphic rocks are formed by heat and pressure changing one type of rock into another type of rock.
• Metamorphic rocks form near lava intrusions, at plate subduction zones, and in deep mountain roots.
Metamorphic rocks - Formation
• Lava intrusions can provide heat that causes metamorphic rocks to form. These small areas of metamorphic rock form from contact metamorphosis.
Metamorphic rocks - Formation
• Rocks that metamorphose because of increasing heat and pressure found at plate subduction zones and in deep mountain roots form large areas of metamorphic rock through regional metamorphosis.
Metamorphic rocks - Classification
• Metamorphic rocks are classified into 2 major groups:– Foliated– Nonfoliated
Metamorphic rocks - Classification
• Foliated rocks form when differential pressure causes minerals to form in layers.
• These rocks will have stripes or planes that they will break easily along.
• These “stripes” don’t usually line up with the original bedding planes in sedimentary rocks.
Metamorphic rocks
• Nonfoliated metamorphic rocks formed in areas where the pressure from all sides was equal, so there is no “linear” quality to the rocks.
Metamorphic rocks - Formations
• Structures and formations seen in metamorphic rocks include:– Folding– Plastic deformation– Stretching– Alternating dark and
light layers (gneissic foliation)
Metamorphic rocks - Examples
• Some common types of metamorphic rock include:– Slate– Schist– Gneiss– Amphibolite– Marble– Quartzite– Metaconglomerate
Metamorphic rocks - Charted
Metamorphic rocks - story
• What do you know about the history of the Earth in the place where this rock was found?