Rocks Objective(s): List and describe the three types of rocks, their properties, and how they are formed

3 Categories of Rock Igneous Sedimentary Metamorphic What determines the category a rock will be? How it is formed

Igneous Rock Formation Melting and solidification of molten rock material Lava Cools outside the Earth = EXTRUSIVE Magma Cools inside the Earth = INTRUSIVE Lava Magma

Texture CRYSTAL SIZE IN IGNEOUS ROCKS Coarse Grained = BIG CRYSTALS Fine Grained = SMALL CRYSTALS Glassy = NO CRYSTALS FORM

Coarse Grained

Fine Grained

Glassy

Vesicular Gas Pockets Pumice Basalt Vesicles are small holes that form when gas escapes into the atmosphere as the lava cools. Pumice cools so fast gas is Trapped inside creating many Holes like a hard sponge

Cooling Rates of Igneous Rocks The rate at which a rock from molten material cools will determine its texture Cools Quickly = Smaller Crystals ON EARTH’S SURFACE - Extrusive Cools Slowly = Larger Crystals BELOW EARTH’S SURFACE - Intrusive

Sedimentary Rock Formation Most sedimentary rocks are formed by compression and cementation of sediment SEDIMENTS = Other pieces of other rocks and minerals

Sedimentary Rocks Some sedimentary rocks are made up of particles of pre-existing rocks and minerals that were deposited by wind or water and cemented together

Cementation Particles are cemented together by minerals precipitated out of solution as water evaporates Conglomerate Sandstone Siltstone What do you notice is different about each example? Particle size

Compaction or Compression Very small sediments are compressed by the pressure of the overlying sediments, or water Become bonded together without cement Ex – Shale

Other Sedimentary Rocks Chemical Precipitation Minerals once dissolved in water precipitate out as a result of evaporation of seawater Ex – Limestone, Dolostone, Gypsum, and Salt Limestone Dolostone Gypsum Salt

ORGANIC Sedimentary Rocks From something once living Ex – Coal = Dead Plant Matter Limestone = Shell fragments (hard parts) of dead organisms

DO NOW: How are rocks classified? Once a rock is created does it stay that way forever?

Metamorphic Rock Formation Original rock form has been changed by heat and pressure Recrystallization: Rearrangement of crystals usually forming larger crystals ANY ROCK can be metamorphosed to become a metamorphic rock

Example: Shale  Slate  Phyllite Shist Limestone  Marble

Changes of Metamorphism New minerals form More dense Less porous Distortion of rock-bending that destroys original structures Such as fossils or pebbles

Foliation Thin bands or lines of aligned minerals, known as BANDING It is caused by the re-grouping of minerals into light and dark layers within the rock Banding is used to identify metamorphic rocks

Properties of Igneous Rock 1. Contain crystals (size tells how quickly the rock cooled) 2. Some appear glassy due to rapid cooling. 3. Many different colors NOT in bands. 4. No fossils

Properties of Sedimentary Rock 1. Composed of many sediments, some different sizes, some same size. 2. May contain fossils 3. May have distinct layers 4. Color appears dull or earthy

Properties of Metamorphic Rock 1. Bands of light and dark color due to foliation 2. May show signs of bending or distortion 3. Crystals are flattened, not large like igneous rock. 4. No fossils 5. No pores or openings

Definition and Important Facts of Geology ROCK CYCLE Definition and Important Facts of Geology

ANY ROCK TYPE CAN BE CHANGED INTO ITSELF OR ANY OTHER TYPE OF ROCK!! Rock Cycle The processes involved in destroying old rocks and creating new ones REMEMBER: ANY ROCK TYPE CAN BE CHANGED INTO ITSELF OR ANY OTHER TYPE OF ROCK!!

Important Facts About Geology Nearly all rocks form from other rocks Exceptions are Organic Rocks Rocks are classified by how they were formed Rock types remain stable for millions of years

Rock Cycle http://www.classzone.com/books/earth_science/terc/content/investigations/es0602/es0602page02.cfm?chapter_no=investigation.swf

Do Now Describe how each rock type is formed