Rocks and

the Rock Cycle

To get you thinking…

• What natural process

is responsible for the

appearance of these

rocks?

Bell Ringer

Name the 3 types of rock.

Is one type of rock able to change into a

different type of rock?

Rocks and the Rock CycleThree Major Types of Rock

Igneous Rock – formed when lava or magma cools and crystalizes

Sedimentary Rock –formed from cemented sediments as a result from weathering and erosion

Metamorphic Rock –formed from igneous or sedimentary rocks that undergoes tremendous heat and pressure

Rocks and the Rock CycleThe Rock Cycle

Any of the three major types of rock can be changed into another of the three types.

Rock Cycle – the series of processes in which rock forms, changes from one type to another, is destroyed, and forms again by geological processes

Much of the rock in the Earth’s continental crust has probably passed through the rock cycle many times during Earth’s history.

Rocks and the Rock Cycle

Rocks and the Rock Cycle

Rocks and the Rock Cycle

Rocks and the Rock Cycle

Rocks and the Rock Cycle

Rocks and the Rock Cycle

Rocks and the Rock Cycle

Igneous Rock Formation

Igneous rock – form when lava or magma cools and

crystallizes

Magma – molten rock below Earth’s surface

Lava – magma that flows onto Earth’s surface

Igneous Rocks

Magma formation

There are four main factors involved in the formation of

magma.

Temperature – must be high enough to melt rock

Pressure – as pressure increases, the melting point

increases

Water content – changes the melting point of rocks, as

water content increases, the melting point decreases

Mineral content – changes the melting point of rocks

Igneous Rocks

Mineral content

Different minerals have different

melting points.

Rocks rich in iron and

magnesium melt at higher

temperatures

Rocks rich in silicon melt at

lower temperatures

Igneous Rocks

Basalt

Granite

Partial melting

Partial melting – the process whereby some minerals

melt at relatively low temperatures while other

minerals remain solid

This occurs because different minerals have

different melting points (determined by the chemical

composition of the mineral).

When minerals melt, a certain type of magma is

formed.

Igneous Rocks

Partial melting

Igneous Rocks

What can we infer about the melting point of Quartz?

Fractional Crystallization

When magma cools, it crystallizes in the reverse order of

partial melting

Fractional crystallization – the first minerals to

crystallize are the last minerals that melt

When minerals solidify, a certain type of magma is

formed.

Igneous Rocks

Fractional Crystallization

Igneous Rocks

Mineral Composition of Igneous rocks

Intrusive rocks – formed when magma cools and

crystallizes below Earth’s surface

Generally contain larger crystals due to slower

cooling of magma

Intrusive rocks with large crystals are also called

coarse-grained igneous rocks

Igneous Rocks

Intrusive Rocks

Igneous Rocks

Granite Diorite

Mineral Composition of Igneous rocks

Extrusive rock – formed when magma cools and

crystallizes on Earth’s surface

Generally contain smaller crystals due to faster

cooling of magma

Extrusive rocks with small crystals are called fine-

grained igneous rocks.

Igneous Rocks

Extrusive Rocks

Igneous Rocks

Basalt Rhyolite

Mineral Composition of Igneous Rock

There are three families of igneous rock

Felsic rock – igneous rock that is generally light in

color and contains a lot of silica and feldspar

Also called granitic rock

Igneous Rocks

Igneous Rocks

Pumice

Granite

Rhyolite

Mineral Composition of Igneous Rock

Mafic rock – igneous rock that is generally dark in

color and contains a lot of magnesium and iron

Also called basaltic rock

Igneous Rocks

Igneous Rocks

Scoria

Gabbro

Basalt

Mineral Composition of Igneous Rock

Intermediate rock – igneous rock that contains less

silica than felsic rock but more than mafic rock

Igneous Rocks

Igneous Rocks

Obsidian

Andesite

Diorite

Texture

Texture – refers to the size, shape, and distribution

of the crystals or grains that make up a rock

Igneous Rocks

Rhyolite

(fine-grained)Granite

(coarse-grained)

Obsidian

(glassy)

Porphyritic rocks

Porphyritic texture – rock characterized by large,

well-formed crystals surrounded by finer-grained

crystals of the same mineral or different minerals

Igneous Rocks

Diorite Andesite

Vesicular rocks

Vesicular texture – rock characterized by a spongy

appearance

Holes called vesicles are left behind as gases are

trapped in thick magma

Igneous Rocks

Pumice Scoria

End of Igneous Rocks