ROCKS

What is a Rock? Naturally-occurring mixtures of minerals, mineraloids (no crystals), or organic matter.

Types of Rocks… The three main kinds of rock are igneous, sedimentary and metamorphic rock. Igneous rock: forms when magma/lava cools and hardens Sedimentary rock: forms when sediments are buried, compacted & cemented together Metamorphic rock: forms when existing rock is subjected to great heat & pressure over a long period of time

What is the difference between a rock and a mineral? Rocks are made up of ONE or MORE minerals.

Once a rock is formed, does it stay the same rock forever? NO!

Rocks are continually changed by many processes, such as weathering, erosion, compaction, cementation, melting, and cooling Rocks can change to and from the three types

What is the process through which rocks change? The Rock Cycle—earth materials change back and forth among the different types of rocks

No set path a rock takes to become another kind of rock

IGNEOUS METAMORPHIC SEDIMENTARY Weathering, Erosion, Compaction, Cementation Recrystallization Melting, Solidification Melting, Solidification Recrystallization SEDIMENTARY METAMORPHIC Weathering, Erosion, Compaction, Cementation

How are rocks redistributed? The core, mantle, & crust are one giant rock recycling machine

“Ignis” = Latin for “fire” Igneous Rocks “Ignis” = Latin for “fire” Formed from the cooling of either magma or lava The most abundant type of rock Classified according to their origin and composition Igneous Rocks come from magma/lava cooling down.

ORIGIN— Where rocks are formed Below ground = from magma (intrusive igneous rock) Usually have LARGE crystal grains (they cooled slowly) Cooling could have taken hundreds of years.

Some have large & small crystals (called porphyritic)

Above ground = from lava (extrusive igneous rock) Usually have SMALL or NO crystals (they cooled too quickly)

Granite: Intrusive or Extrusive? Why?

Obsidian: Intrusive or Extrusive? Why?

COMPOSITION— What kind of substances or minerals are rocks made of

Basaltic Igneous Rocks —made from lava/magma that is low in silica, rich in iron and magnesium. Rocks are dark-colored.

Granitic Igneous Rocks—made from magma/lava high in silica and oxygen Granitic Igneous Rocks—made from magma/lava high in silica and oxygen. Rocks are light-colored.

Andesitic Igneous Rocks—have a composition between basaltic and granitic.

Diorite-has course grains

Basalt-no course grains

Granite

Sedimentary Rocks Formed from sediments (rock fragments, mineral grains, animal & plant remains-shells, bones, leaves, stems) that are pressed or cemented together or when sediments precipitate out of a solution.

Sedimentary rocks are fossil-carrying rocks. These sediments are moved by wind, water, ice or gravity then deposited into layers. Sedimentary rocks represent 7% of the Earth’s crust, but they cover 70% of the Earth’s surface. Sedimentary rocks are fossil-carrying rocks.

What turns sediments into solid rock? Water or wind breaks down and deposits sediment (erosion & deposition) Elements of Erosion are heat, cold, rain, waves, and grinding ice.

At first sediments fit together loosely, over long periods of time, thick layers build up. Because of the heavy layers, the upper layers press down on the layers below them, causing Compaction.

Dissolved minerals flow between the particles and cement them together (cementation)

How can sedimentary layers help us understand the age of fossils? As sedimentary rocks are deposited, they form horizontal layers Scientists know that the layers on top (and the fossils in the top layer) are YOUNGER than the fossils in lower layers.

3 Types of Sedimentary Rocks: Clastic (also called Detrial)—made of broken pieces of other rocks. Formed when rock fragments are squeezed together.

Clastic-Sedimentary Rocks Shale: Formed from tiny particles of clay compacted together. Sandstone: Forms from the compaction and cementation of small particles of sand.

Clastic-Sedimentary Rocks Conglomerate: Formed from fragments of various sizes of rocks and pebbles. Fragments are rounded because they have been worn along riverbeds. Breccia: Fragments are jagged with sharp edges. Formed from various size of rocks and pebbles.

3 Types of Sedimentary Rocks: Organic—remains of plants and animals are deposited in thick layers Organic refers to substances that once were part of living things or were made by living things which contain calcite or calcium carbonate. (Can be tested by using acid)

Organic-Sedimentary Rocks Coal: Remains of swamp plants buried in water or by volcanic ash. Limestone: Formed by hard shells of once living things such as coral, clams, oysters, and snails. When they die their shells pile up and are covered by other sediments compacting and cementing them.

Types of Limestone Chalk-can be naturally occurring and in rock form. Coquina-made of large fragments of shells.

3 Types of Sedimentary Rocks: Chemical—minerals dissolved in lakes, seas, or underground water. Can occur when lakes evaporate.

Chemical-Sedimentary Rocks Rock Salt: Made of the mineral halite. Gypsum: Formed by evaporation in dry climates.

Rocks that have changed due to intense temperature and pressure Metamorphic Rocks Rocks that have changed due to intense temperature and pressure “Meta” means “change” and morphosis means “form” in Greek Igneous, sedimentary and other metamorphic rocks can change to become metamorphic rocks

What occurs in the Earth to change these rocks? Pressure from overlying rock layers High heat, but not enough to melt the rock Rocks may be flattened or bent or atoms may be exchanged to form new minerals.

*You can think of metamorphic rocks as a squished peanut butter & jelly sandwich in your lunch.

Where do metamorphic rocks usually form? Where magma intrudes relatively cool rock Near colliding plates (near mountain ranges) Places that are covered miles thick with other rock causing pressure When hot water intrudes rock Where a meteorite strikes Earth (rare) Where lightning bolts strike rocks (rare)

How are metamorphic rocks classified How are metamorphic rocks classified? Look at Pages 162-163 in your books Foliated—mineral grains are flattened and line up in parallel bands Example: gneiss formed from rearrangement of minerals in granite into bands

How are metamorphic rocks classified? Non-Foliated—No bands are formed Example: marble formed from limestone

Rocks Transformed Limestone Marble Shale Slate

Rocks Transformed Sandstone Quartzite Gneiss or Mudstone Schist

Say you have an unknown rock how do you classify it? Color: Like with minerals, color alone does not provide enough information to identify a rock.

Say you have an unknown rock how do you classify it? Texture can be very useful. Look at and feel the rocks surface. Some are smooth and glassy others are rough and chalky. Grain Size: Large or Small Grain Shape: Fine Grained or Jagged Grain Patterns: Flat Layers, Wavy, banded, or random. No Visible Grain: Some cool to fast to have grains.

Say you have an unknown rock how do you classify it? Mineral composition: By looking under a microscope, a geologist can identify the minerals it contains. You can use acid to check for carbonates. (Limestone or Chalk)

Say you have an unknown rock how do you classify it? Origin: Where it came from! Metamorphic: Usually have bigger crystals because of increased heat and pressure. Igneous: Usually is made up of very large particles. Sedimentary: Small solid pieces of material that come from rocks or living things. (Smoother)

Rock Cycle Animations Rock Cycle Quiz Rock Cycle Animation #1 Weathering and Erosion Quiz Rock Cycle Video (Made by a Middle School Student) Go to the next slide to play Jeopardy.

Jeopardy Game The Rock Cycle

The Rock Cycle Igneous Rocks 10 pts 10 pts 10 pts 10 pts 20 pts 20 pts Metamorphic Rocks Sedimentary Rocks 10 pts 10 pts 10 pts 10 pts 20 pts 20 pts 20 pts 20 pts 30 pts 30 pts 30 pts 30 pts 40 pts 40 pts 40 pts 40 pts 50 pts 50 pts 50 pts 50 pts

Question 1 Rock Mixture of minerals, volcanic glass, organic matter, or other material Check Answer

Question 2 Rock Cycle A model showing the processes that create and change rock. Check Answer

Question 3 Sedimentary Rock _________ rock can be changed by heat and pressure into metamorphic rock. Check Answer

Question 4 Igneous __________ rock can be broken into fragments that may later form sedimentary rock. Check Answer

Question 5 Metamorphic ______ rock can melt and cool to form igneous rock. Check Answer

Question 6 Lava Magma reaches the surface flows from a volcano as ____________ . Check Answer

Question 7 Intrusive Magma trapped below the surface forms large – grained ______________ rock when it cools. Check Answer

Question 8 Extrusive Magma cooling at or near Earth’s surface forms small-grained __________ igneous rock. Check Answer

Question 9 Intrusive and extrusive Igneous rocks are classified in 2 ways. ______________ Check Answer

Question 10 cool Volcanic glass rock __________ so quickly that few crystals form. Check Answer

Question 11 Heat and pressure _____________ and ______________ result from one layer of rock on top of another layer. Check Answer

Question 12 magma Sometime temperature and pressure are great enough to melt rock, forming ______________. Check Answer

Question 13 Foliated texture _____________ texture – mineral grains flatten and line up in parallel layers or bands. Check Answer

Question 14 Nonfoliated texture _______ texture - mineral grains grow and rearrange but do not form layers. Check Answer

Question 15 Pressure Sometimes ____________ flattens mineral grains in rocks without melting them. Check Answer

Question 16 Sedimentary Rock Type of rock mostly found on the exposed surface of Earth. Check Answer

Question 17 layers Sedimentary Rocks form in __________ . Check Answer

Question 18 sediments Rock fragments, mineral grains, and bits of plants and animal remains moved by wind, water, ice or gravity are called _________________. Check Answer

Question 19 cementation When water and other minerals move through open spaced between larger sediments, gluing them together, ____________ occurs. Check Answer

Question 20 Organic sedimentary _________ ___________ rocks are made from the remains of once – living plants or animals. Check Answer