Formation of Igneous Rocks Formation of Igneous Rocks

Formation of Igneous Rocks

Formation of Igneous Rocks • • Location Source – Molten Rock • Composition – • • (3 Components) 1. Liquid 2. Solid 3. Volatiles Creation Composition 1. 2. 3. • Juvenile Material Remelting Rock Water/Volatile Addition Roll of Temperature and Pressure – Beneath Surface (Intrusive) • Magma • Very-slow cooling • Large Crystals – At Surface (Extrusive) • Lava • Slow cooling • Small Crystals – Above Surface (Extrusive) • • • Pyroclastics Very-fast cooling Exposure to air Exposure to water No Crystals

MAGMA CRYSTALIZATION

Where Igneous Rocks Form

Igneous Rock Formation Magma • Molten rock beneath earth’s surface • It is less dense than surrounding rock, so it rises (like ice in a Coke®) Lava • Molten rock at or near earth’s surface • As molten rock cools, it forms IGNEOUS ROCK

Igneous Rock Formation INTRUSIVE igneous rock – Forms when magma cools and hardens beneath the earth’s surface. – Coarse (large) grained rock, because the crystals (xtls) have more time to grow – EX: granite, diorite, gabbro

Igneous Rock Formation EXTRUSIVE igneous rock – Forms when lava cools and hardens near the earth’s surface. – Fine (small) grained rock, because the crystals (xtls) don’t have time to grow very large – EX: rhyolite, andesite, basalt

Igneous Rock Formation PYROCLASTIC Igneous Rock • Forms when lava cools instantly as it hits air or water at the surface of the earth • No crystals at all • May have holes (porous) because gases don’t have time to escape before lava cools. • EX: scoria, pumice, obsidian

PYROCLASTIC scoria, obsidian, pumice EXTRUSIVE rhyolite andesite basalt INTRUSIVE granite, diorite, gabbro

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