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?