What is a Rock?• Naturally-occurring mixtures of minerals, mineraloids, glass or organic matter.
What is a Rock?• Rocks are divided into 3 groups based on how they were formed: • IGNEOUS • SEDIMENTARY • METAMORPHIC
What is the difference between a rock and a mineral?• Rocks are made up of ONE or MORE minerals.
What is the process through which rocks change?• The Rock Cycle— earth materials change back and forth among the different types of rocks
• 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 different types
The Rock CycleThis is only one pathway through the rock cycle!
There is no set path a rock takes to become another kind of rock
Now you complete aRock Cycle diagram.Identify the Rock Typesformed by writing thename ins the ovals. IGNEOUS Weathering, Erosion, Compaction, Recrystallization Cementation Melting, Solidification Melting, Solidification Recrystallization SEDIMENTARY METAMORPH Weathering, Erosion, IC Compaction, Cementation
How are rocks redistributed?• The core, mantle, & crust are one giant rock recycling machine !
Questions--1. What do igneous rocks form from?2. What kind of rock are fossils found?3. What are metamorphic rocks formed by?Remember: The rock cycle is a continuous process that occurs over millions of years. It makes new rock, destroys old rock, and recycles the ingredients of the Earths crust over and over again!
• “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
ORIGIN— Where rocks are formed• Below ground = from magma (intrusive igneous rock) • Usually have LARGE crystal grains (they cooled slowly)
Some have large & small crystals(called porphyritic)Above ground = from lava (extrusiveigneous rock)Usually have SMALL or NO crystals(they cooled too quickly)
COMPOSITION— What kind of substances the rocks are 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. Rocks are light-colored.• Andesitic Igneous Rocks—have a composition between basaltic and granitic.
• Formed from sediments (rock fragments, mineral grains, animal & plant remains) that are pressed or cemented together or when sediments precipitate out of a solution.
• These sediments are moved by wind, water, ice or gravity.• 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)
• The heavy sediments press down on the layers beneath (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. http://youtu.be/9Df4CtlZ0AQ
3 Types of Sedimentary Rocks:• Clastic (also called Detrial)—made of broken pieces of other rocks.• Organic—remains of plants and animals are deposited in thick layers – Examples: Fossil rich limestone is made from the shells of ocean animals; used to make chalk• Chemical—minerals dissolved in lakes, seas, or underground water
Examples• Limestone made when calcite mineral precipitates from sea water• Rock Salt— made from evaporation of sea waters
• 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.
How are metamorphic rocks classified?1. Foliated—mineral grains are flattened and line up in parallel bands – Example: gneiss formed from rearrangement of minerals in granite into bands
2. Non-Foliated—No bands are formed– Example: marble formed from limestone
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)
Final Vocabulary Words• Uplift: The rising of regions of the Earth’s crust to higher elevations.• Strata: layers of Rock.• Fossils: The trace or remains of an organism that lived long ago, commonly preserved in sedimentary rocks.• Magma: Molten material on the inside of Earth’s crust.• Lava: molten material on Earth’s surface.
Vocabulary Review• Foliated: A metamorphic rock in which the mineral grains are arranged in planes or bands.• NonFoliated: a metamorphic rock in which the mineral grains are NOT arranged in planes or bands.• Index Fossils: a fossil found in the rock layers of only one geological age and that is used to establish the age of the rock layers.
Vocabulary Review• Stratification: The process in which sedimentary rocks are arranged in layers.• Coal: a fossil fuel that forms underground from partially decomposed plant material.
Vocabulary Review• Rock Cycle: the series of processes in which a rock forms, changes from one type to another, is destroyed, and forms again by geological processes.• Rock: a naturally occurring solid mixture of one or more minerals or organic matter.• Erosion: the process by which sediment is moved from one location to another.• Weathering: process by which rock is broken down into smaller pieces.
Vocabulary Review• Sediment: small solid particles of rock and inorganic/organic material.• Sedimentary Rock: a type of rock formed when particles from other rocks or the remains of organisms are compacted and cemented together.• Deposition: the process by which sediment is “dropped” and comes to rest.• Cementation: process by which dissolved minerals crystallize and glue particles of sediment together.
Vocabulary Review• Compaction: the process by which sediments are pressed together.• Igneous Rock: a type of rock that forms from the cooling of magma or lava.• Metamorphic Rock: a type of rock formed from existing rock changed by heat, pressure, or chemical reactions.