Rocks! 6/21/2016 AF Carpinelli 1

What’s a rock??? A rock is any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet. Three Types: – Igneous – Metamorphic – Sedimentary 6/21/2016 AF Carpinelli 2

Rock Types Defined Igneous Rocks: –Formed when magma cools and hardens beneath the Earth’s surface or on top of the Earth’s surface as a result of volcanic eruptions. 6/21/2016 AF Carpinelli 3

Rock Types Defined Sedimentary Rocks - Product of Weathering: Process in which rocks are broken down by water, air and living things to produce sediment; - Sediment is made of weathered pieces of earth material; - Eventually, sediment is compacted and cemented to form sedimentary rocks. 6/21/2016 AF Carpinelli 4

Metamorphic Rocks –Under extreme pressure and temperature conditions, sedimentary rocks will change into metamorphic rocks. –If metamorphic rocks are subjected to even higher temperatures, they may melt to form magma! –The magma will eventually crystallize to form igneous rocks once again! 6/21/2016 AF Carpinelli 5 Rock Types Defined

Relationships Among the Rocks? The Rock Cycle explains the relationships among the different rock types. 6/21/2016 AF Carpinelli 6

The Rock Cycle 6/21/2016 AF Carpinelli 7

6/21/2016 AF Carpinelli 8 The Rock Cycle Source of Energy: Igneous and Metamorphic Rocks: Heat from the Earth’s Interior Sedimentary Rock: External Processes (Weathering and movement of weathered material) powered by energy from the sun and gravity.

6/21/2016 AF Carpinelli 9 Igneous Rocks

6/21/2016 AF Carpinelli 10 Igneous Rock

6/21/2016 AF Carpinelli 11 What is an Igneous Rock? Crystalline (made of crystals) Forms from the cooling of magma or lava Made of silicates

6/21/2016 AF Carpinelli 12 What is Magma? Melted (or partially melted) rock Rock melts when its temperature exceeds the melting point of one or more minerals within the rock Can contain dissolved gases like water vapor or carbon dioxide

6/21/2016 AF Carpinelli 13 Types of Magma Basaltic – rich in mafic minerals, low in silica (45-55%); low gas content; low viscosity (resistance to flow); high temperature (1000 – 1200 C)

6/21/2016 AF Carpinelli 14 Types of Magma Andesitic – intermediate in mafic minerals; intermediate in silica (55-65%); intermediate in gas content, viscosity, and temperature (800 – 1000 C)

6/21/2016 AF Carpinelli 15 Types of Magma Rhyolitic - poor in mafic minerals, high in silica (more than 65%); high gas content; high viscosity; low temperature (650 – 800 C)

6/21/2016 AF Carpinelli 16 Classes of Igneous Rocks Igneous rocks are classified in two ways: –Texture (aphanitic, phaneritic, porphyritic, vesicular, glassy) –Composition (ultramafic, mafic, intermediate, felsic)

6/21/2016 AF Carpinelli 17 Extrusive/Intrusive Rocks

6/21/2016 AF Carpinelli 18 Textures The texture of igneous rock is based on the way it cooled. –Extrusive rocks cool quickly and so the crystals do not have time to grow large Called aphanitic (fine-grained) texture Example  (basalt)

6/21/2016 AF Carpinelli 19 Textures –Intrusive rocks cool more slowly Results in larger (sometimes very large) crystals Called phaneritic (coarse- grained) texture Example  (granite)

6/21/2016 AF Carpinelli 20 Other Textures Although aphanitic and phaneritic textures are the most common, there are others. –Glassy – like glass (extrusive) – cools extremely fast –Vesicular – contains air bubbles (extrusive) – frothy – cools fast

6/21/2016 AF Carpinelli 21 Other Textures

6/21/2016 AF Carpinelli 22 Other Textures –Porphyritic – contains a mixture of small and large crystals – occurs when an extrusive lava is covered before it cools completely, allowing remaining crystals to grow large –Pegmatitic – very slow cooling magma – extremely large crystals (very rare)

6/21/2016 AF Carpinelli 23 Other Textures

6/21/2016 AF Carpinelli 24 Composition of Igneous Rocks All igneous rocks are made of silicates Range from ultramafic (containing little silica and mostly mafic minerals) to felsic (containing mostly silica and little mafic minerals) Composition dramatically changes the color of the rock

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6/21/2016 AF Carpinelli 26 Composition of Igneous Rocks Ultramafic Mafic Intermediate Felsic

6/21/2016 AF Carpinelli 27 Classifying Igneous Rocks Igneous rocks are classified by both their composition and texture –For example – a felsic rock with an aphanitic texture would be…

6/21/2016 AF Carpinelli 28 Classifying Igneous Rocks Rhyolite!

6/21/2016 AF Carpinelli 29 Comparing Igneous Rocks