An Introduction

What does a rock want to be when it grows up? A ROCK STAR

We’ve already learned about something called the WATER CYCLE so we know a cycle is a process that REPEATS

There are three types of rocks: Igneous Lava Sedimentary Metamorphic Sediments Magma Pool

The Rock Cycle . . . is a group of changes The ROCK CYCLE is NOT a circular cycle but rather a process by which one rock changes into another which can take billions of years.

What do you do to a baby rock? ROCK IT!

Most of the Earth’s crust is made up of rock Did you know? Most of the Earth’s crust is made up of rock Rocks are made up of one or more minerals and have been formed by heat or pressure in the earth 95% of the Earth’s crust is igneous rock and metamorphic rock Sedimentary rock is less than 5% of the Earth’s crust but it covers 75% of the Earth’s continental surface

Classification Rocks are classified by: 1. How they were formed 2. Composition – what the rock is made up of 3. Textures – sizes, shapes, and positions of grains

The ROCK CYCLE M M C H/P Metamorphic W/E H/P Sedimentary Magma C/C W/E Sediments W/E Igneous M = Melting W/E = Weathering & Erosion C = Cooling H/P = Heat & Pressure C/C = Compacting & Cementing

What is a rock’s favorite cereal? Cocoa Pebbles

Rock that forms from the cooling of magma or lava Igneous Rock Rock that forms from the cooling of magma or lava

Magma

Origins – How rock melts 1. Temperature increases 2. Composition changes = lowers the melting point of the rock 3. Pressure on rock decreases (pressure released)

Composition & Textures The amount of time it takes for magma or lava to cool determines the texture Glue or paste your Composition & Texture table in this section of your foldable

Formation of Igneous Rocks Pyroclasts Extrusive Intrusive Porphyry: partially crystalline Fig. 5.3

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.

How Igneous Rock Is Formed Igneous rocks are called fire rocks and are formed either underground or above ground

Intrusive Igneous Rock Split the section labeled ROCK FORMATION into two sections Intrusive Igneous Rock Underground – Inside Magma becomes trapped in small pockets Magma cools SLOWLY underground - bakes Usually coarse-grained

Extrusive Igneous Rock Above ground - Outside Formed when volcanoes erupt Magma above the earth is called lava Lava cools QUICKLY above ground and in water Usually fine-grained

Magma is molten rock that is Magma forms “intrusive” igneous rock deep underground Magma forms “intrusive” igneous rock

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 of the eruption of Stromboli volcano

Sedimentary Rock Rock that forms when sediments are compacted and cemented together

Origins of Sedimentary Rock Erosion - bits of earth washed downstream and settles to the bottom of the rivers, lakes, and oceans. Eroded earth is deposited on top of each other. Layers are pressed down and turn into rock

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.

Composition Clastic – rock & mineral fragments stick together. The size & shape influences their name

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.

This stream carries sediment that has weathered from mountains in Alaska

Sediment (A) may someday become a clastic rock (B) if compacted and cemented together.

2. Chemical Sedimentary Rock - Forms when minerals crystallize out of a solution like sea water and becomes rock

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.

These pebbles were deposited in a stream that once flowed over this area in Indiana, USA thousands of years ago.

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.

3. Organic Sedimentary Rock - Forms from the remains of organisms

Coquina

Structures Features tell the story of formation Layers are called strata Strata differs depending on the kind, size and color of the sediment The rate of deposition can affect the thickness of layers What could affect the rate of deposition (deposits)? The amount of rain – more = flooding & less = drought Weathering (wind & water) affects the design of sedimentary rock

Weathering (wind & water) affects the design of sedimentary rock

The pre-existing rock is often referred to as the Metamorphic Rock Rock that forms when the texture and composition of pre-existing rock CHANGES due to heat or pressure The pre-existing rock is often referred to as the “Parent Rock”

Origins of Metamorphic Rock Rocks that have “MORPHED” into another kind of rock Contact Metamorphism – Rock comes into “contact” with magma and cooks 2. Regional Metamorphism – Enormous pressure builds up in deeply buried rock

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.

The more you try to be gneiss, the more you get taken for granite!

Composition Scientist understand the history of the rock based on the minerals present and how they have changed

Textures Metamorphic rock is described by two types of textures: Foliated and Non-foliated Foliated – 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

Start Apply increasing heat & pressure Finish

Here's a chart of some of the key characteristics that can help you identify the rocks within these three main classes.

Crystals: Small, flat surfaces that are shiny or sparkly, like tiny mirrors. Fossils: Imprints of leaves, shells, insects, or other 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 of different colors in the rock. Sand or pebbles: Individual stones, pebbles, or sand grains visible in the rock.

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 3. How it formed Igneous rock is classified by composition - being light or dark but we use what words? Mafic or Felsic Igneous 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

Sedimentary rock is classified by composition – how it was formed in one of three ways. What are the three ways? 1. Clastic 2. Chemical 3. Organic Metamorphic 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

Igneous rock forms how? From the cooling and solidification of lava or magma Sedimentary rock forms how? From the erosion and weathering of rock What type of rock can become sedimentary rock? All types Metamorphic rock forms how? From intense heat & pressure changing pre-existing rock

The ROCK CYCLE M M C H/P Metamorphic W/E H/P Sedimentary Magma C/C W/E Sediments W/E Igneous M = Melting W/E = Weathering & Erosion C = Cooling H/P = Heat & Pressure C/C = Compacting & Cementing

The END!