Chapter 6 rocks

Sec 6.1

Rocks and the Rock Cycle

#1 The solid part of the Earth is rock.

• Rock can be many different things, but geologists have classified rocks into three major types by the way the rocks form.

#2 The solid part of the Earth is rock.

• Three major Types of Rock

– Igneous rock (such as granite and basalt)

– Sedimentary rock (such as sandstone and limestone)

– Metamorphic rock (such as slate and marble)

The solid part of the Earth is rock.

Igneous rock (such as granite and basalt)

The solid part of the Earth is rock.

Sedimentary rock (such as sandstone and limestone)

The solid part of the Earth is rock.

Metamorphic rock (such as slate and marble)

#3 The solid part of the Earth is rock.

• Existing rock can be changed by:

Pressure

Heat

Chemical processes

#4 The solid part of the Earth is rock.

• The series of processes in which rock forms, changes from one type to another, is destroyed, and forms again by geological processes is called the rock cycle.

#5 Igneous Rock

• A starting point in the rock cycle would be with igneous rock.

• Igneous rock forms when magma or molten rock cools and hardens.

• Magma is the molten rock from volcanoes. Magma is called lava when it is exposed at the Earth’s surface.

Big pile of Igneous Rock

• A starting point in the rock cycle would be with igneous rock.

• Igneous rock forms when magma or molten rock cools and hardens.

• Magma is the molten rock from volcanoes. Magma is called lava when it is exposed at the Earth’s surface.

#6 Igneous Rock

• Igneous is Latin for “from fire”.

• When the igneous rock is exposed on the Earth’s surface weathering begins.

• The weathering is a process of breaking down rock at zones of weakness.

• Huge igneous rock structures have zones of weakness called joints.

#7 Bowen’s Reaction series

• As the magma cools certain minerals tend to crystallize first. This generally happens in the same order. As the minerals form, they remove specific elements from the magma. This process changes the magma’s composition.

Bowen’s Reaction series

• Think about vegetable beef soup. If you remove water, the soup will have a stronger taste. If you remove the beef, you are left with a vegetable soup.

Bowen’s Reaction series

• Bowen’s reaction series is the simplified pattern that illustrates the order in which minerals crystallize from cooling magma according to their chemical composition and melting point.

• See page 127

#8 Sedimentary rock

• All rock breaks down into smaller and smaller fragments. The smallest are knows as sediments.

• Sedimentary rock forms when deposits of dirt and rock are cemented and harden.

• The zones of weakness in sedimentary rock are along layers.

Layers of Sedimentary rock

#’s 9 & 10 Metamorphic rock

• Metamorphic rock forms when existing rock is altered. Metamorphic means “changed form”.

• The forces and processes the change existing rock:

• Tremendous pressure

• Extreme heat

• Chemical processes

Marble is a Metamorphic rock

Marble is a Metamorphic rock

Marble is a Metamorphic rock

#11 Class Discussion

• Extreme heat would cause rock to become metamorphic rock. What would it be if even more heat was added?

#11 Class Discussion

• Extreme heat would cause rock to become metamorphic rock. What would it be if even more heat was added?

• If enough heat was added so that the rock melted it would become igneous

#12 Rock Cycle

• Rock doesn’t have to go through the cycle in order. Any of the type of rock can be changed into another, even into a different form of the same type. For example, sedimentary rock can weather and be changed into a different type of sedimentary rock.

Rock Cycle

#14 Properties of Rocks

• The physical and chemical properties of rocks tell us where and how a rock was formed.

• We will study each type in different sections of this chapter.

Properties of Rocks

• Chemical stability is the measure of the tendency of a chemical compound to maintain its original chemical composition rather than break down to form a different chemical.

• We learned in the last chapter that the chemical stability of minerals is dependent on the number of bonds between the elements silicon (Si) and oxygen (O).

#’s 15 & 16 Properties of Rocks

• Physical stability is determined by how and where the rock was formed. Rocks tend to break down along the zones of weakness.