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Rocks, Rocks and Rocks, Rocks and More Rocks!More Rocks!
Igneous – Igneous – ““FIRE ROCKSFIRE ROCKS””
(for now)(for now)
Extrusive Igneous RocksExtrusive Igneous Rocks Notes: Notes: Extrusive Igneous RocksExtrusive Igneous Rocks
form when lava erupts from a volcano form when lava erupts from a volcano or or ““bubbles upbubbles up”” from tectonic plates from tectonic plates moving apart - moving apart - ontoonto Earth Earth’’s surface.s surface.
Ex: Ex: BasaltBasalt – the – the most common most common extrusiveextrusive rock on Earth; forms most rock on Earth; forms most of Earthof Earth’’s ocean floor.s ocean floor.
Ex: Ex: Obsidian Obsidian – black volcanic glass– black volcanic glass
Igneous RocksIgneous Rocks Earth's Most Abundant Earth's Most Abundant Bedrock: BasaltBedrock: Basalt
Basalt forms more of Basalt forms more of Earth's surface than Earth's surface than any other rock type. any other rock type. Most areas in ocean Most areas in ocean basins are basalt. basins are basalt.
May be on land from May be on land from lava flows, too. lava flows, too.
Igneous Rock - ObsidianIgneous Rock - ObsidianObsidian was used to make knives, arrow heads, spear points, scrapers and many other weapons and tools
How igneous rocks form…How igneous rocks form…
ExtrusiveWhen a volcano erupts or when magma bubbles to the surface
Intrusive when magma cools slowly inside earth
Intrusive Igneous RocksIntrusive Igneous Rocks Notes: forms when magma hardens Notes: forms when magma hardens
beneathbeneath Earth Earth’’s surface (INSIDE).s surface (INSIDE).
Ex: Ex: GraniteGranite – the most – the most abundantabundant intrusiveintrusive rock on Earth rock on Earth’’s continents.s continents.
Forms the core of many mountain Forms the core of many mountain ranges.ranges.
Ex: Ex: Porphyry-Porphyry- looks like jello w/fruit looks like jello w/fruit inside it inside it
Intrusive Igneous Intrusive Igneous RocksRocks
GraniteGranite is used to make many
objects
Granite is also well-known from its many world-famous natural exposures.
These include: Stone Mountain, GA; Mount Rushmore, SD
Intrusive Igneous RockIntrusive Igneous Rock
Porphyry
Igneous RocksIgneous Rocks Notes: Texture – fine grainedNotes: Texture – fine grained
Rapidly Rapidly cooling lava forms a cooling lava forms a finefine--grained rock with grained rock with small small crystals.crystals.
Ex: Ex: BasaltBasalt - crystals too small to be - crystals too small to be seen without a microscope.seen without a microscope.
Ex: Obsidian –smooth, shiny texture Ex: Obsidian –smooth, shiny texture like thick glass & cooled without like thick glass & cooled without forming crystals forming crystals ““Volcanic GlassVolcanic Glass””
Igneous RocksIgneous Rocks
ObsidianObsidian
Obsidian on the side of a volcano
Igneous RocksIgneous Rocks Notes: Texture: coarse-grainedNotes: Texture: coarse-grained
Slowly Slowly cooling magma forms cooling magma forms coarsecoarse--grained rock with grained rock with large large crystalscrystals
Ex: granite and porphyryEx: granite and porphyry
Igneous Rocks – Igneous Rocks – Mineral CompositionMineral Composition
Notes:Notes:
When magma is When magma is highhigh in silica in silica light-light-colored rockscolored rocks form - like granite. form - like granite.
When lava is When lava is lowlow in silica in silica dark-dark-colored rockscolored rocks form - like basalt form - like basalt
High Silica vs. Low SilicaHigh Silica vs. Low Silica
Uses of Igneous RockUses of Igneous Rock
Notes:Notes:
GraniteGranite – Statues, Bridges and old – Statues, Bridges and old public buildings, Paving streets with public buildings, Paving streets with cobblestone, floors, kitchen cobblestone, floors, kitchen countertops (thin polished sheets of countertops (thin polished sheets of Granite)Granite)
Uses of Igneous RockUses of Igneous Rock
BasaltBasalt - Gravel for construction - Gravel for construction
ObsidianObsidian - Sharp tools for cutting and - Sharp tools for cutting and scraping (Native Am!), Starting scraping (Native Am!), Starting vegetable gardens (fertilizer) – itvegetable gardens (fertilizer) – it’’s s called Perlite, which is formed from called Perlite, which is formed from heating Obsidianheating Obsidian
Pumice is cool! It can float!Pumice is cool! It can float!
Pumice – used for cleaning and Pumice – used for cleaning and polishing polishing
Uses of Igneous RockUses of Igneous Rock
Statues, Public Buildings - GraniteStatues, Public Buildings - Granite
Uses of Igneous RocksUses of Igneous Rocks
Cobblestone streets, kitchen Cobblestone streets, kitchen countertops – Granite countertops – Granite
Questions…Questions… What processes form Igneous Rocks?What processes form Igneous Rocks? How are the 2 types of Igneous Rock How are the 2 types of Igneous Rock
different?different? How can we use Igneous Rocks? How How can we use Igneous Rocks? How
have they been used in the past?have they been used in the past? Can you describe the most common Can you describe the most common
Intrusive Ign. Rock? Where is it Intrusive Ign. Rock? Where is it commonly found?commonly found?
Can you describe the most abundant Can you describe the most abundant Extrusive Ign. Rock? What area on Extrusive Ign. Rock? What area on Earth is mostly made of this type?Earth is mostly made of this type?