What is the difference between Rocks and Minerals? A rock is any group of minerals bound together.

ROCKS IGNEOUS ROCKS SEDIMENTARY ROCKS METAMORPHIC ROCKS Rocks have been shaped by early humans into tools and weapons. Rock is used still in buildings, monuments, and roads. Ancient Egyptian pyramids were made of limestone rock.

Intro to Minerals and Rocks https://www.youtube.com/watch?v=XEg_XuCMD2s

ROCKS ARE CLASSIFIED BY THEIR COMPOSITION AND TEXTURE: Composition - is the combination of elements or compounds that make up a rock. Composition is determined by its minerals. Different minerals form under different conditions.

ROCKS ARE CLASSIFIED BY THEIR COMPOSITION AND TEXTURE: Texture – the size, shape and position of the grains that make up a rock Each grain in the rock is made from a mineral. The grains in a rock can be different colours, shapes and sizes. Each grain in the rock is made from a mineral. The grains in a rock can be different colours, shapes and sizes.

Porous Texture Small holes or spaces between the grains in rocks are called PORES If a rock contains these small holes it is said to be POROUS. If the holes are connected, then the rock is PERMEABLE and fluids can flow through the rock.

GRAINS CAN BE EITHER: INTERLOCKING GRAINS ROUNDED GRAINS: Eg. Granite                                Eg. Sandstone Each grain in the rock is made from a mineral. The grains in a rock can be different colours, shapes and sizes.

ROCKS WITH INTERLOCKING GRAINS Grains fit tightly together Less likely to absorb water Non-porous Harder Eg. Granite

ROCKS WITH ROUNDED GRAINS Have gaps between the grains so are more like to ABSORB WATER More POROUS SOFTER and more crumbly Eg. Sandstone Each grain in the rock is made from a mineral. The grains in a rock can be different colours, shapes and sizes. Rocks with rounded grains are more likely to absorb water than rocks with interlocking grains. This is because the water can get into the gaps between the grains. Rocks that absorb water are called porous. Rocks with rounded grains are usually softer and more crumbly than rocks with interlocking grains. So porous rocks tend to be softer than non-porous rocks. Rocks with interlocking grains are more likely to be hard and non-porous

Rounded Quartz Grains

Igneous Rocks

Igneous means “firey”. Igneous rocks are formed by the COOLING (and thus crystallization) of molten rock called magma Molten rock is often called magma or lava. The difference between magma and lava is….. No fossils or organic matter in igneous rocks

Magma: is molten rock under the earth’s crust Magma: is molten rock under the earth’s crust. Lava: is molten material that has erupted out of a volcano. As molten rock cools, different minerals are created. The minerals that are created depend on the type of elements and compounds that are available. As mineral crystals grow, these minerals interlock and create different types of rock.

TWO TYPES OF INGNEOUS ROCKS Igneous rocks are formed from lava or magma. MAGMA is molten rock that is UNDERGROUND LAVA is molten rock that erupts out on the SURFACE  

INTRUSIVE OR PLUTONIC IGNEOUS ROCKS: Form UNDERGROUND Have DISTINCTIVE mineral grains very HARD.  Crystals are LARGER  . Eg Granite.

EXTRUSIVE OR VOLCANIC IGNEOUS ROCKS Form when lava cools (on the surface) Generally LACK distinctive mineral grains. Crystals are SMALLER  Eg. Pumice, obsidian.

How are Igneous Rocks Classified? We classify igneous rocks based on two characteristics: Composition and Texture As molten rock cools, different minerals are created. The minerals that are created depend on the type of elements and compounds that are available. As mineral crystals grow, these minerals interlock and create different types of rock.

Composition is based on the TYPE of minerals in the rocks. The types of minerals determine the COLOUR of the rocks. Based on composition there are TWO main groups of igneous rocks:   

Composition Mafic Rocks: Rich in elements such as: Magnesium, Iron, Calcium Magma is hotter, thinner, more fluid. Mafic Rocks are dark in colour Most volcanic rocks are mafic 

TWO MAIN GROUPS OF IGNEOUS ROCKS MAFIC ROCKS – contain more MAgesium and iron  (MAgesium    +     FERRIC – refers to iron  = MAFIC) Magnesium and iron are dark minerals so Mafic Igneous Rocks are usually DARK in colour. 

Composition: Felsic Rocks Are rich in Feldspar and Silicon minerals and elements such as Sodium, Potassium, Aluminum. Magma has high amounts of silica, making it thick and slow. Light in colour Most plutonic rocks are felsic

FELSIC ROCKS contain more FELDSPAR and SILICON These minerals are LIGHTER  in colour

TEXTURE Texture depends on the size, shape and arrangement of the crystals.  Crystal size is the MOST important factor affecting texture. Depends on the RATE of cooling of magma LONGER COOLING TIME = LARGER CRYSTALS Range from glassy-smooth (eg obsidian), to coarse-grained eg granite.

Crystal Size What would affect the RATE of cooling?

Crystal Size What would affect the rate of cooling? WHERE the magma cools Where do we find magma?

Rocks with smaller crystals Smaller Crystals form when melted rock cools QUICKLY, there is LESS TIME for crystals to form therefore only very small crystals form, giving a fine-grained texture. 

ROCKS WITH LARGE CRYSTALS Intrusive rocks (Plutonic rocks) form BELOW the surface and therefore cool SLOWER, allowing more time for crystals to form. Therefore plutonic rocks have coarse grains. Eg. granite 

So what kind of rocks would you expect to have smaller crystals?

Intrusive Rocks: Extrusive Rocks Crystal Size LARGER crystals Magma cools slowly below surface Eg. Granite, diorite, gabbro, pegmatite, and peridotite. SMALLER Crystals  Lava cools quickly on the surface, leaving less time for crystals to form yielding FINE GRAIN TEXTURE Eg. Basalt Crystal Size

Texture: Glassy smooth Obsidian (also known as volcanic glass) It is a dark, extrusive igneous rock formed when molten rock is rapidly cooled on the earth’s surface.

Texture – Coarse- grained Eg. granite

Porous When lava with lots of water and gasses leave a volcano, the gas bubbles escape. Eg. PUMICE is known to have many vesicles and air pockets. Pumice is also sold at the body shop. People rub it on their skin to make their skin smoother.

Porphyritic Texture Rocks that have large crystals surrounded by fine-grained mass of rock Caused by DIFFERENT COOLING STAGES May have both large and small crystals. Indicates that the magma sat and cooled a bit below the Earth's surface, thus giving time for the large crystals to grow, before erupting onto the surface and cooling very quickly. surface and cooling very quickly. The large crystals are termed phenocrysts while the aphanitic rest of rock is called the groundmass.

FAMILIES OF IGNEOUS ROCKS: Granite GRANITE  forms from PLUTONIC, FELSIC Magma FELSIC – light coloured Contain mostly ORTHOCLASE FELDSPAR and QUARTZ,  Other minerals that may be present: Mica, and Hornblende

FAMILIES OF IGNEOUS ROCKS: GABBRO GABBRO FAMILY Magma cools slowly underground (PLUTONIC) Dark (Mafic), more dense than Granite Family Most common igneous rocks found on ocean floor Eg. BASALT

FAMILIES OF IGNEOUS ROCKS: DIORITE FAMILY This families characteristics are a BLEND of composition and colour somewhere between the other two families Coarse-grained Contain less quartz than granite does Less dark than Gabbro Eg. Andesite

Where are igneous Rocks Formed? Volcanoes, Near VOLCANOES

Mid Ocean Ridges, Mid-Ocean Ridges, Subduction Zones, Deep within crust

Subduction Zones,

Deep within Crust

SQUAMISH Squamish, B.C. is a very popular destination for rock climbers. A lot of this rock is granite, which is a felsic, intrusive igneous rock.

Uses of Igneous Rocks Granite is very strong - used for BUILDING and CONSTRUCTION, head stones and kitchen counter tops. 

Uses of Igneous Rocks PUMICE is lightweight and has lots of air spaces and has an abrasive nature. Used by cosmetic and cleaning industries to make things like excess skin removing stones.

Batholiths Batholiths are very large masses of intrusive igneous rock (plutonic rock) that forms and cools deep in the Earth's crust. almost always made mostly of felsic or intermediate rock types.

Stocks igneous intrusion that has surfaced Smaller, less than 100 square km. 

Pyroclastic Flow a hot (typically >800 °C), chaotic mixture of rock fragments, gas, and ash that travels rapidly (tens of meters per second) away from a volcanic vent or collapsing flow front.  Pyroclastic flows can be extremely destructive and deadly because of their high temperature and mobility.

Phaneritic Texture

Homework Read p63-68 Answer 3-7, p68