The Rock Cycle

The Rock Cycle

Igneous Rock

Sedimentary RockMetamorphic Rock

SedimentMagma

Weathering & Erosion

Weathering & Erosion

Cementation & Compaction

Melting

Melting

Cooling

Heat, Pressure and/or Chemical Fluids

Heat, Pressure and/or Chemical Fluids

Melting

THREE TYPES OF ROCKS

• Sedimentary Rocks:Formed in layers, the result of accumulated sediments

that have been compressed together.

• Igneous Rocks:Formed from the cooling of molten rock.

• Metamorphic Rocks:Formed from older "parent" rock (either igneous or

sedimentary) under intense heat and/or pressure.

Sediment

When all types of rock erode over time, sediment is formed: sand, clay, stones, etc.

Sedimentary RocksSedimentary rock is formed by sediment (sand, silt, gravel…) compacted together.Below: Sandstone from P.E.I.

Right: Conglomerate in St-John’s, Newfoundland

Cementation & Compaction400 million years ago, sediment was deposited at the bottom of the Champlain Sea that once covered Ottawa. It was later compacted & compressed to form limestone & sandstone.

If you go to Hog’s Back, you will notice the ripple marks that were made by the ancient waves.

Layering

As you see here, layering is a common feature of sedimentary rocks.

Igneous Rock

Igneous rock is molten rock (magma or lava) that has solidified.

Here are two pieces of granite. As the magma cooled down, it crystallized forming granite.

The size of the crystals is determined by the cooling period. The longer the cooling period, the larger the crystals are.

Another exampleObsidian is the result of volcanic lava coming in contact with water. Often the lava pours into a lake or ocean and is cooled quickly. This process produces a glassy texture in the resulting rock, avoiding the crystalline texture as in granite.Iron and magnesium give the obsidian a dark green to black colour.

Metamorphic Rocks

Agents of Metamorphism

Changes occur because of:

• Heat

• Pressure

• Chemical fluids

Metamorphism means "changed form".

Slate

Marble

Metamorphism

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.

Gneiss - (pronounced "nice") - a banded or striped rock with alternating layers of dark and light minerals. The dark layers commonly contain biotite, and the light layers commonly contain quartz and feldspar.

Granite