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

Classification MAFIC FELSIC Determined by the minerals they contain Felsic and Mafic Felsic contains lighter elements such as silica and oxygen Mafic contains heavier elements such as iron and calcium they tend to be darker in color MAFIC FELSIC

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

Coarse Grained

Fine Grained

Glassy Cooled too quickly for crystals to form

Vesicular Gas Pockets Pumice Scoria 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 http://geology.com/rocks/igneous-rocks.shtml

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

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

Clastic Sedimentary Rocks Clastic 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

Non-Clastic 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 http://geology.com/rocks/sedimentary-rocks.shtml

Top part of the table are the clastic rocks, bottom are the nonclastic Cemented Cemented Cemented Compacted Compacted Chemical (Precipitated) Chemical (Precipitated) Chemical (Precipitated) Chemical and Organic Organic

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 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 http://geology.com/rocks/metamorphic-rocks.shtml

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

DO NOW: Complete the table below on your handout Rock Type How did it form? Physical features Igneous Melting and solidification of molten rock material Crystals glassy Many colors (not in bands) No fossils Sedimentary compression and cementation of sediment Sediments May have layers May have fossils Dull, earthy colors Metamorphic changed by heat and pressure Bands of color May be bent or wavy No pores/openings

Sample Letter Name of Rock This Rock is _______ A Obsidian Igneous B Conglomerate Sedimentary C Basalt D Slate Metamorphic E Sandstone F Gneiss G Pumice H Schist

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 (Bioclastic) Rocks Rocks are classified by how they were formed Rock types remain stable for millions of years

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