7 Most of the Earth’s crust is made up of rock Did you know?Most of the Earth’s crust is made up of rockRocks are made up of one or more minerals andhave been formed by heat or pressure in the earth95% of the Earth’s crust is igneous rock andmetamorphic rockSedimentary rock is less than 5% of the Earth’s crustbut it covers 75% of the Earth’s continental surface
8 Classification Rocks are classified by: 1. How they were formed 2. Composition – what the rock is made up of3. Textures – sizes, shapes, and positions of grains
20 Formation of Igneous Rocks PyroclastsExtrusiveIntrusivePorphyry:partiallycrystallineFig. 5.3
21 Granite rocks are igneous rocks which were formed by slowly cooling pockets of magma that were trapped beneath the earth's surface. Granite is used for long lasting monuments and for trim and decoration on buildings.Scoria rocks are igneous rocks which were formed when lava cooled quickly above ground. You can see where little pockets of air had been. Scoria is actually a kind of glass and not a mixture of minerals.Pumice rocks are igneous rocks which were formed when lava cooled quickly above ground. You can see where little pockets of air had been. This rock is so light, that many pumice rocks will actually float in water. Pumice is actually a kind of glass and not a mixture of minerals.Obsidian rocks are igneous rocks that form when lava cools quickly above ground. Obsidian is actually glass and not a mixture of minerals.
22 How Igneous Rock Is Formed Igneous rocks are called fire rocksandare formed either undergroundorabove ground
23 Intrusive Igneous Rock Split the section labeled ROCK FORMATION into two sectionsIntrusive Igneous RockUnderground – InsideMagma becomes trapped in small pocketsMagma cools SLOWLY underground - bakesUsually coarse-grained
24 Extrusive Igneous Rock Above ground - OutsideFormed when volcanoes eruptMagma above the earth is called lavaLava cools QUICKLY above ground and in waterUsually fine-grained
25 Magma is molten rock that is Magma forms “intrusive” igneous rock deep undergroundMagma forms “intrusive” igneous rock
26 Lava forms “extrusive” igneous rock Basalt is an extrusive igneous rock that is very dark in color.It is the most common type of rock in the Earth's crust and it makes up most of the ocean floor.This is an image ofthe eruption ofStromboli volcano
27 Sedimentary Rock Rock that forms when sediments are compacted and cemented together
28 Origins of Sedimentary Rock Erosion - bits of earthwashed downstream andsettles to the bottom of therivers, lakes, and oceans.Eroded earth is depositedon top of each other.Layers are pressed down andturn into rock
29 Sandstone rocks are sedimentary rocks made from small grains of the minerals quartz and feldspar. They often form in layers as seen in this picture. They are often used as building stones.Limestone rocks are sedimentary rocks that are made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells. This rock is used in concrete and is an excellent building stone for humid regions.Shale rock is a type of sedimentary rock formed from clay that is compacted together by pressure. They are used to make bricks and other material that is fired in a kiln.
30 Composition Clastic – rock & mineral fragments stick together. The size & shape influences their name
31 Cathedral Rock in Arizona is made of a clastic rock called sandstone Cathedral Rock in Arizona is made of a clastic rock called sandstone. . These rocks are more than 250 million years old and are now being weathered and eroded away by the creek.The rocks that make high ridges are much more resistant to weathering than the surrounding rocks.
32 This stream carries sediment that has weathered from mountains in Alaska
33 Sediment (A) may someday become a clastic rock (B) if compacted and cemented together.
34 2. Chemical Sedimentary Rock - Forms when minerals crystallize out of a solution like sea water and becomes rock
35 Conglomerate rocks are sedimentary rocks Conglomerate rocks are sedimentary rocks. They are made up of large sediments like sand and pebbles. The sediment is so large that pressure alone cannot hold the rock together; it is also cemented together with dissolved minerals.Gypsum rocks are sedimentary rocks made up of sulfate mineral and formed as the result of evaporating sea water in massive prehistoric basins. It is very soft and is used to make Plaster of Paris, casts, molds, and wallboards.
36 These pebbles were deposited in a stream that once flowed over this area in Indiana, USA thousands of years ago.
37 Ripples in beach sand , such as those in the upper photograph (A) may someday become a rock like the sandstone in the lower photograph (B).This sandstone was part of a beach over 200 million years ago in the Triassic period.
38 3. Organic Sedimentary Rock - Forms from the remains of organisms
40 Structures Features tell the story of formation Layers are called strataStrata differs depending on the kind, size andcolor of the sedimentThe rate of deposition can affect the thickness of layersWhat could affect the rate of deposition (deposits)?The amount of rain – more = flooding & less = droughtWeathering (wind & water) affects the design ofsedimentary rock
41 Weathering(wind & water) affectsthedesignofsedimentary rock
42 The pre-existing rock is often referred to as the Metamorphic RockRock that forms when the texture and composition of pre-existing rock CHANGES due to heat or pressureThe pre-existing rock is often referred to as the“Parent Rock”
43 Origins of Metamorphic Rock Rocks that have“MORPHED”into another kind of rockContact Metamorphism – Rock comes into “contact” with magma and cooks2. Regional Metamorphism – Enormous pressure builds up in deeply buried rock
45 Schist rocks are metamorphic Schist rocks are metamorphic. These rocks can be formed from basalt, an igneous rock; shale, a sedimentary rock; or slate, a metamorphic rock. Through tremendous heat and pressure, these rocks were transformed into this new kind of rock.Gneiss rocks are metamorphic. These rocks may have been granite, which is an igneous rock, but heat and pressure changed it. You can see how the mineral grains in the rock were flattened through tremendous heat and pressure and are arranged in alternating patterns.
46 The more you try to be gneiss, the more you get taken for granite!
47 CompositionScientist understand the history of the rock based on the minerals present and how they have changed
48 TexturesMetamorphic rock is described by two types of textures: Foliated and Non-foliatedFoliated – minerals are aligned and look like pages in a book (A distinct pattern)2. Non-Foliated – minerals don’t appear to be in any pattern
50 Here's a chart of some of the key characteristics that can help you identify the rocks within these three main classes.
51 Crystals: Small, flat surfaces that are shiny or sparkly, like tiny mirrors.Fossils: Imprints of leaves, shells, insects, orother items in the rock.Gas bubbles:"Holes," like Swiss cheese, in the rock.Glassy surface: A shiny and smooth surface, like colored glass.Ribbon-like layers: Straight or wavy stripes ofdifferent colors in the rock.Sand or pebbles: Individual stones, pebbles, orsand grains visible in the rock.
52 Review: There are how many types of rocks? 3 Rocks are put in one of these categories (classified) by three things. What are they?1. Composition 2. Texture How it formedIgneous rock is classified by composition - being light or dark but we use what words?Mafic or FelsicIgneous rock is classified by texture – coarse-grained or fine-grained but we use words to describe where they formed. What words do we use?Intrusive or Extrusive
53 Sedimentary rock is classified by composition – how it was formed in one of three ways. What are the three ways?1. Clastic Chemical OrganicMetamorphic rock is classified by composition – What minerals are present and by texture – but we describe the texture based on the presence of a pattern or a lack of a pattern. What words do we use to describe the pattern or lack of a pattern?Foliated or Non-foliated
54 Igneous rock forms how?From the cooling and solidification of lava or magmaSedimentary rock forms how?From the erosion and weathering of rockWhat type of rock can become sedimentary rock?All typesMetamorphic rock forms how?From intense heat & pressure changing pre-existing rock
55 The ROCK CYCLE M M C H/P Metamorphic W/E H/P Sedimentary Magma C/C W/E SedimentsW/EIgneousM = Melting W/E = Weathering & ErosionC = Cooling H/P = Heat & Pressure C/C = Compacting & Cementing