Rocks & The Rock Cycle Unit D, Chapter 2. Introduction Questions 1.How can rocks change? 2.What will...
-
Upload
maud-walker -
Category
Documents
-
view
217 -
download
0
Transcript of Rocks & The Rock Cycle Unit D, Chapter 2. Introduction Questions 1.How can rocks change? 2.What will...
Rocks & The Rock Cycle
Unit D, Chapter 2
Introduction Questions
1. How can rocks change?2. What will cause rocks to change?3. How long will it takes rocks to change?4. What will the rocks change/turn into?5. Where do these changes occur?6. What is a cycle?7. What is the rock cycle?
Igneous Rocks
UD, C2, Section 1, pD40-45
Minerals
• Rocks divided into 3 types – how they formed– Igneous– Sedimentary– Metamorphic
• Rocks build landforms– Mountains– Volcanoes, etc.
• Minerals build rocks
Minerals
• Minerals: solid substance with a definite chemical composition and physical structure– Form as crystals• Solids with regular geometric shape
– Shows how atoms are arranged inside of it
– 4000 different minerals (12 common)
Minerals
• Properties: (characteristics)– Hardness • Diamond – Hardest
– Can scratch other substances
• Talc – Softest– Fingernail can scratch it
– Color– Crystal shape– Color of the streak when rubbed on tile– Density (mass ÷ volume)
Formation of Igneous Rocks
• Magma: melted rock inside the Earth– Heat and pressure in mantle melts rock
• Lava: melted rock that reaches Earth’s surface
Formation of Igneous Rocks
• Igneous rock: forms when magma is pushed up from the mantle into the cool crust or onto the surface and hardens into rock– Crystallization: another name for hardening into
rock
Formation of Igneous Rocks
• Intrusive:– Magma hardens under the surface– Cools slowly (millions of years) forming large crystals– Examples: Diorite, Granite, Gabbro
• Landforms:– Shiprock, New Mexico• Magma cooled underground “pluton”• Weathering & erosion wears away softer rock around it• Exposes “batholith”
Formation of Igneous Rocks
• Extrusive:– Lava hardens on the surface– Cools quickly forming small/no crystals– Examples: Rhyolite, Andesite, Basalt, • Obsidian – glassy rock without crystals• Pumice – full of small holes, can float
Uses of Igneous Rocks
• Igneous rocks some of most common on Earth– Granite used as a building material• Looks nice, resists weathering
– Obsidian used for tools, jewelry, and mirrors• Breaks with sharp edges, looks nice, glassy surface
– Pumice used as scouring substance in soaps/cleaners• Can be pounded into powder
– Igneous rocks are the source of many ores• Chromium, platinum, diamond, nickel, copper
– Ore: useful minerals/mixtures or minerals that are mined
Sedimentary Rocks
UD, C2, Section 2 pD48-53
Formation of Sedimentary Rocks
• Mostly found on surface (75%)(5% all crust)• Weathering: process of breaking rock into
smaller pieces– Natural processes:• Flowing water• Moving ice• Freezing & thawing (contraction & expansion)• Growth of plants
• Erosion: movement of sediment to new place
Formation of Sedimentary Rocks
• Deposition: dropping of sediment– Wind or water when it slows down• Slower means less kinetic energy to carry sediment
– Ice when it melts
• Sedimentation: build up of sediment layers over millions of years– Weight of layers compact (packs down) sediments
• Cementation: glues packed particles together
Formation of Sedimentary Rocks
• Two main groups of sedimentary rocks– Clastic rocks: made of sediments that were
weathered, transported, and deposited in layers– Chemical rocks: formed from minerals that were
dissolved in water, came out of solution, and deposited
Clastic Rocks
• Clastic rocks classified by the size of sediments– Fine particles: Shale
• Most common sedimentary rock• Often contain fossil imprints
– Medium particles: Sandstone• Most sandstone contains the mineral: Quartz
– Coarse, pebble-sized particles:• Smooth edges: Conglomerate
– Transported long distances to smooth edges
• Sharp edges: Breccia– Transported short distance, didn’t have time to round edges
Chemical Rocks
• Chemical weathering– Rocks breaks down into chemicals that dissolve
• Like sugar dissolving in tea/coffee
• Chemical rocks form in two ways– Evaporation leaves sedimentary rocks behind
• Layer of salt at the bottom of dried-up lake
– Animal shells or skeletons can also form rocks• Coral take chemicals out of water – make limestone reefs• Shells pile up, compacted, cemented – form Limestone
– Limestone far from coast – clue to where ancient seas were
Uses of Chemical Rocks
• Sedimentary rocks make building materials– Bricks, tile, pottery, china from Shale & Mudstone– Many building made from Sandstone– Plaster made from rock Gypsum– Food seasoned & preserved with Rock salt / Halite– Snow & ice on roads melted with Rock salt / Halite– Important energy reserves – petroleum & natural gas– Farmers use ag lime treat acidic soil from Limestone– Fertilizer made from Potassium salts / Phophate rocks
Uses Sedimentary Rocks
• Fossils most likely to lie in sedimentary rocks– Scientists observe fossils• Piece together information of life long ago
– Dinosaurs
Metamorphic Rocks
UD, C2, S3 pD56-61
Formation of Metamorphic Rocks
• Metamorphic rocks not common on the surface– Form inside Earth’s crust– Forces inside Earth lift them up– Weathering wears away rock on top of them
• Metamorphism: process when any kind of rock is changed into metamorphic rock– Inside Earth– Intense heat & pressure change properties of rocks– Depends on “parent rock” & amount heat and pressure
Formation of Metamorphic Rocks
• Metamorphism occurs under two conditions:– Regional metamorphism• Most common
– Plates collide with tremendous pressure– Rock crumples and folds forming mountains– Metamorphic rock in their centers
– Contact metamorphism• Occurs deep in the crust and under volcanoes
– Magma rises and touches rock– Rock “bakes” changing properties
Formation of Metamorphic Rocks
• Metamorphic rocks classified into two groups– Foliated• Layers or bands you can see
– Gneiss
– Nonfoliated• Do not appear layered
– Marble
Processes That Cause Metamorphism
• Heat most important cause of metamorphism– Deeper in Earth’s crust, the hotter it gets• 20-60°C hotter per kilometer of depth• If rock gets too hot it melts
– Source of igneous rock
• Heat breaks chemical bonds allowing new crystallization
Processes That Cause Metamorphism
• Pressure another cause of metamorphism– Deeper in Earth’s crust, the more pressure there is
• Weight of all rock & soil above rock presses down• Crustal movement squeezes rock & bends it
– Heat softened the rock already making it easier to bend
• Extremely hot water can cause metamorphism– Mineral-rich water near magma (300-500°C)
• Minerals added/taken away from rock– Gold, silver, copper often deposited in these rocks
• Texture & minerals of rock tell how it was formed
Uses of Metamorphic Rocks
• Metamorphic rocks used in parts of buildings– Marble used in statues & public buildings
• Beautiful & durable
– Slate used for roofs, chalkboards, floors, and pavement stones• Splits easily into thin sheets
– Talc used for lubrication, cosmetics, dusting powder• From schist easy to make into a powder
– Graphite used as pencil “lead” & lubricants• Another mineral from some metamorphic schists
The Rock Cycle
UD, C2, S4 pD64-67
The Rock Cycle
• Rock cycle: shows processes where rocks are formed from each other– A way Earth recycles its rocks
• All rock was igneous to begin– Earth was molten rock early in history and it cooled– Wind, water, ice started weathering/eroding rock
• Formed sedimentary rock
– Heat & pressure deep in earth and millions of years• Changed rock to metamorphic rock
– Rocks changing between these three ever since
The Rock Cycle
• Five main groups of processes– Melting:
• All three rock types melt forming magma
– Cooling & solidification: • Magma cools forming igneous rock
– Weathering, erosion, deposition: • All three rock types form sediments that are deposited
– Cementation & compaction: • Sediment is cemented and compacted forming sedimentary rock
– Heat & pressure: • All three rock types changed to metamorphic rock
The Rock Cycle & Plate Boundaries
• Oceanic – Continental Convergent Boundary– Sedimentary rock• Sediment deposited where rivers end
– Metamorphic rock• Igneous & sedimentary rock carried down• Rock melted as it continues to sink• Magma rises in cracks & bakes rock around it
– Igneous rock • Rising or erupting magma cools
How Fossils Form
Additional Slides
How a Fossil Forms
• Most fossils form when living things die.
How a Fossil Forms
• Next, the organism is buried by sediment.
How a Fossil Forms
• The sediment slowly hardens into rock and preserves the shapes of the organisms.
How a Fossil Forms
• The sediment slowly hardens into rock and preserves the shapes of the organisms.