2What is a Rock?Naturally-occurring mixtures of minerals, mineraloids (no crystals), or organic matter.
3Types of Rocks…The three main kinds of rock are igneous, sedimentary and metamorphic rock.Igneous rock: forms when magma/lava cools and hardensSedimentary rock: forms when sediments are buried, compacted & cemented togetherMetamorphic rock: forms when existing rock is subjected to great heat & pressure over a long period of time
4What is the difference between a rock and a mineral? Rocks are made up of ONE or MORE minerals.
5Once a rock is formed, does it stay the same rock forever? NO!
6Rocks are continually changed by many processes, such as weathering, erosion, compaction, cementation, melting, and coolingRocks can change to and from the three types
7What is the process through which rocks change? The Rock Cycle—earth materials change back and forth among the different types of rocks
12How are rocks redistributed? The core, mantle, & crust are one giant rock recycling machine
13“Ignis” = Latin for “fire” Igneous Rocks“Ignis” = Latin for “fire”Formed from the cooling of either magma or lavaThe most abundant type of rockClassified according to their origin and compositionIgneous Rocks come from magma/lava cooling down.
14ORIGIN— 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.
15Some have large & small crystals (called porphyritic)
16Above ground = from lava (extrusive igneous rock) Usually have SMALL or NO crystals (they cooled too quickly)
26Sedimentary RocksFormed 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.
27Sedimentary 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.
28What 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.
29At 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.
30Dissolved minerals flow between the particles and cement them together (cementation)
31How can sedimentary layers help us understand the age of fossils? As sedimentary rocks are deposited, they form horizontal layersScientists know that the layers on top (and the fossils in the top layer) are YOUNGER than the fossils in lower layers.
323 Types of Sedimentary Rocks: Clastic (also called Detrial)—made of broken pieces of other rocks. Formed when rock fragments are squeezed together.
33Clastic-Sedimentary Rocks Shale: Formed from tiny particles of clay compacted together.Sandstone: Forms from the compaction and cementation of small particles of sand.
34Clastic-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.
353 Types of Sedimentary Rocks: Organic—remains of plants and animals are deposited in thick layersOrganic 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)
36Organic-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.
37Types of Limestone Chalk-can be naturally occurring and in rock form. Coquina-made of large fragments of shells.
383 Types of Sedimentary Rocks: Chemical—minerals dissolved in lakes, seas, or underground water. Can occur when lakes evaporate.
39Chemical-Sedimentary Rocks Rock Salt: Made of the mineral halite.Gypsum: Formed by evaporation in dry climates.
40Rocks that have changed due to intense temperature and pressure Metamorphic RocksRocks that have changed due to intense temperature and pressure“Meta” means “change” and morphosis means “form” in GreekIgneous, sedimentary and other metamorphic rocks can change to become metamorphic rocks
41What occurs in the Earth to change these rocks? Pressure from overlying rock layersHigh heat, but not enough to melt the rockRocks may be flattened or bent or atoms may be exchanged to form new minerals.
42*You can think of metamorphic rocks as a squished peanut butter & jelly sandwich in your lunch.
43Where do metamorphic rocks usually form? Where magma intrudes relatively cool rockNear colliding plates (near mountain ranges)Places that are covered miles thick with other rock causing pressureWhen hot water intrudes rockWhere a meteorite strikes Earth (rare)Where lightning bolts strike rocks (rare)
45How are metamorphic rocks classified How are metamorphic rocks classified? Look at Pages in your booksFoliated—mineral grains are flattened and line up in parallel bandsExample: gneiss formed from rearrangement of minerals in granite into bands
46How are metamorphic rocks classified? Non-Foliated—No bands are formedExample: marble formed from limestone
49Say 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.
50Say 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 SmallGrain Shape: Fine Grained or JaggedGrain Patterns: Flat Layers, Wavy, banded, or random.No Visible Grain: Some cool to fast to have grains.
51Say 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)
52Say 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)
53Rock Cycle Animations Rock Cycle Quiz Rock Cycle Animation #1 Weathering and Erosion QuizRock Cycle Video (Made by a Middle School Student)Go to the next slide to play Jeopardy.