Classes of Rock  Igneous rock  Sedimentary rock  Metamorphic rock

 Igneous Rock Means “born of fire” The minerals that form igneous rock come from molten rock deep within he crust and upper mantle. Igneous rocks are often found on the Earth’s surface and also deep within it. Igneous rocks reach the surface in two ways:

Extrusive igneous rocks are formed when molten rock is carried to the surface by volcanic processes. When the lava cools new rock is formed. The Paleozoic (230 million years ago) volcanoes in eastern Canada and the more recent volcanoes (53 million years ago) in Western Canada are both examples of extrusive igneous rock.

Intrusive igneous rocks originate deep in the Earth as molten rock called magma. When the magma cools (still beneath the surface) igneous rock is formed. Erosion gradually wears away rock layers above it, eventually exposing the igneous rock. Granite

The Canadian Shield is an example of intrusive igneous rock (as well as metamorphic rock). It formed millions and even billions of years ago deep within the Earth. Igneous Rocks are classified by the minerals they contain and their surface texture. Crystal size determines the texture of the rock. If the magma cooled slowly the texture is coarse and individual crystals can be clearly observed. These are often intrusive.

If the magma cooled quickly there is little time for large crystals to form so the texture is fine (smoother). Lava coming into contact with air or water form this type of fine textured igneous rock. Lava that flows from an underwater volcano, coming into contact with water form rock with the same texture as glass. Obsidian is extremely hard igneous rock that looks just like black glass.

Large amounts of silica Hardens into light coloured silicate minerals Felsic Magma: Thick and slow-moving Large amounts of silica Hardens into light coloured silicate minerals Ex. Quartz, orthoclase feldspar Mafic Magma: Hot, thin, fast moving Large amounts of iron and magnesium Hardens into dark silicate minerals Ex. Horneblende, biotite

Granite Family form from felsic magmas coarse-grained due to slow, sticky magma cool underground an intrusive igneous rock that can appear at the surface only after being uplifted and top layers are eroded.

Gabbro Family mafic rocks, darker and denser than granite often contains, olivine, pyroxene, plagioclase feldspar basalt is the most common rock in family dark rock on ocean floor or formed in lava flows cooling on land

Diorite Family characteristics of both malfic and felsic colours tend to be medium grey and green

Igneous Intrusions Volcanoes are actually only a small picture of the magma activity that exists below the surface of the earth!

 Sedimentary Rock Sedimentary rocks are not formed from molten magma or lava, but are formed from sediments building up at the bottom of lakes and oceans.

Formation Sediment builds up as layers of material are created by weathering (breaking up of rock) , transported by wind, glaciers, or water, and finally deposited. Layer upon layer accumulates over time, compacting the material beneath it. Water slowly filters through the tightly packed sediment. Dissolved minerals in the water precipitate out, binding or cementing the sediment together.

There are 3 types of Sedimentary rocks: 1. Clastic sedimentary rocks: comprised of broken up pieces of other rocks Non-Clastic 2. Chemical sedimentary rocks: formed from chemicals dissolved in shallow seas or lakes 3. Biogenic sedimentary rocks: formed from the remains of living animals

Clastic Sedimentary Rocks Shale Clastic Sedimentary Rocks Sandstone Fine Course Stones and Boulders Conglomerate

Non- Clastic Chemicals Animals Plants

Chemical Sedimentary Rocks Water containing dissolved minerals evaporates leaving the deposits of chemical sedimentary rocks. The chemistry of Opal is primarily SiO2 and varying amounts of water. The amount of water varies from 5 -10% and greater. This water can help geologists determine the temperature of the host rock at the time the opal formed.

Chemical Rocks! Rock salt (halite) forms when minerals fall out of solution and precipitate.

Organic Rocks! Rock forms from sediments of plant and animal remains. (White Cliffs of Dover)

Biogenic Sedimentary Rocks Limestone and dolomite are the most common forms of biogenic sedimentary rocks formed from the calcium deposits left by shell and skeletal remains of marine creatures. Calcium carbonate cements these fragments together to form limestone. Magnesium carbonate cements the fragments together to form dolomite.

Sedimentary Features Stratification- changes in the type of sediment will result in different layers. Why? Rivers change routes, slow/speed up

Fossils: often found in sedimentary rocks as organisms are buried by sediments on land and in water. Ripple Marks and Mud Cracks: Ripples are formed by wind, current or waves and are preserved when sand becomes sandstone. Mud cracks form when wet clay deposits dry and contract. The cracks fill up with sediment and fossilize when the clay becomes shale.

Metamorphic Rocks “meta” means change “morph” means shape Metamorphic rocks change more than just their shape. They change in mineral composition, structure, and texture as a result of immense heat and pressure. Unlike igneous rocks, where change occurs during melting, metamorphic rocks change while the rock is solid. The degree of change depends on the temperature and pressure.

Metamorphic Rocks There are many more types of metamorphic rocks than igneous or sedimentary rocks combined. In fact, each sedimentary and igneous rock has at least one metamorpnic equivalent. Approximately 85% of the upper crust is made of metamorphic rock. Although most of it is buried under sedimentary rock. Metamorphic rocks are formed wherever there is enourmous pressure and temperatures reach over 300 °C.

Two Types of Metamorphic Rock 1. Contact metamorphic rock  rocks that change form due to heat given off during the formation of intrusive igneous rocks 2. Dynamic metamorphic rock  rocks that form due to the mass of rock layers above them or due to tectonic stresses Metamorphic rocks have a banded structure called foliation - layers of similar minerals.

Foliation - visible bands Gneiss Gneiss banding Slate

Weak Foliation Marble Asbestos veins Serpentinite

Metamorphic Rocks Gneiss Schist Slate Marble

Granite to Gneiss

Becoming Metamorphic Rock