Download ROCKS notes - St. Raymond High School for Boys

ROCKS
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What is a rock?
A rock is a mix of minerals, ______________, glass or organic matter. ALL rocks are made of 2 or more minerals.
II. The Rock Cycle: the process by which rocks are formed over MANY years. It is a __________________ repeating pattern.
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Changes back & forth among ______________________, metamorphic, & sedimentary rocks
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Erosion, weathering, compaction, & cooling can change them
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Also changed by heat & ____________________
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The rock cycle has _________ BEGINNING OR END!!
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The rock cycle demonstrates the relationships among the _____ major rock groups
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It is powered by the interior heat of the Earth
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As well as earth’s momentum and…
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The _________________from the sun
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It involves processes on the Earth’s surface as well as the Earth’s interior
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It connects the “hydrologic cycle” with the “___________________ cycle”.
Classifying Rocks
Rocks are classified by how they formed and what they’re made of
There are 3 general classes of rocks
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Igneous Rocks…are formed when ________ and ______________ crystallize to form solid rock
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Metamorphic Rocks…are formed when an existing rock is partially melted, squeezed, _______________________
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Sedimentary Rocks…are formed when sediments (sand clay, and silt) are compressed and become solid rock
III. Igneous Rocks: Formed by the cooling & solidification of magma & lava resulting in a rock w/inter-grown crystals
A. ________________: hot, melted rock beneath the earth’s surface (1400oC); usually found underground & can be
forced up towards the surface (usually by volcanoes)
B. Lava: ________________ rock from a volcano flowing onto the earth’s surface. This is above ground & cools faster
than magma b/c it’s exposed to cooler temps than magma. Both of these contain crystals…which are MINERALS!!
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There are ____ Types of Igneous Rocks
1. ______________________: magma cools beneath the earth’s surface. Intrusive: Inside the earth. Indicated by
larger mineral grains. Cooling below the earth’s surface is slower & allows the mineral grains to grow larger.
Eg: Granite:
Light-colored, coarse- grained, no pattern
Mostly quartz, feldspar, mica, and hornblende
Often used for buildings and monuments
2. _______________________:
• Formed by lava that cools @ the earth’s surface
• Cooling @ earth’s surface is __________________, not allowing mineral grains & crystals to grow:
smaller mineral grains than intrusive. Or, may have no grains – glassy appearance.
• Extrusive: ____________________ the earth’s surface.
Eg: Obsidian:
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Natural volcanic ________________
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Forms when lava cools ___________________________________
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Usually _____________, but small pieces may be clear
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Fractures along curved (conchoidal) surface
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Used as spear and arrow points, knives
______________________________
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Rock that contains______________pockets
Scoria 
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*** some igneous rocks ___________show crystal patterns. These rocks are referred to as ____________.
C. Classification
Based upon color & density, based upon magma type.
1. Basaltic: dense, heavy, & dark colored. Rich in magnesium (Mg) & iron (Fe); rocks that are formed from basaltic lava
that flows directly from volcanoes. Continental crust.
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Basalt: Dark-colored, fine- grained, extrusive. Formed where lava erupted onto surface. Most widespread igneous
rocks. Found locally in the Palisades along west shore of Hudson River, Connecticut River valley
2. Mafic: Contains heavier elements resulting in a darker color & higher density. Rich in basalt & gabbro(Mg &
Fe).Oceanic crust.
3.
Granitic/andesitic: light colored & lower density than basaltic Has much Si & O2 Flows from volcano. Andestic
composition is between granitic &basaltic
4. Felsic: light colored, rich in feldspar & silica, lower density
D. Mineral Classification in Rock
Steps: ESRT
1. Find the rock on the Igneous Rock Identification Chart
2. Follow the column down to the composition part of the chart & read the minerals.
3. The actual % can be determined by marking the span of the mineral on another piece of paper & then using the
scale of the side diagram.
IV. Sedimentary Rocks: Formed when sediments that were pressed or cemented together or when sediments ppt out of
solution.
A. Terms:
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Sediments: loose material such as rock fragments, mineral grains &/or bits of organic material (plants, bones) are
moved by wind, water, ice, or gravity.
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Weathering: the process that breaks rocks into smaller pieces
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Erosion: the movement of weathered material
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Compaction: occurs when layers of small sediments become compressed by the weight of layers above them.
Pressure from the top pushes down on the bottom.
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Cementation: process in which large sediments are glued together by minerals deposited between sediments.
Water soaks thru the rock & soil, some minerals will dissolve & make sediments stick together.
Sedimentary Rock Layers:
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Often form layers
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Older layers on the bottom – these were deposited FIRST
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More sediments pile up, become compacted & cemented
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Sometimes the layers are disrupted & the older ones are no longer on the bottom
B. Classification
1. Detrial or Clastic: detrial means to “wear away” Rocks made from other rocks broken down by weathering 
compaction & cementation.
a) Clastic texture: “broken” texture
b) Shape & size of sediments: clastic rocks are named according to the size & shape of their sediments:
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Conglomerate: well rounded sediments
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Breccias: sharp angles, not rounded
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Concrete: gravel & grains
Grain size: boulders, cobbles, pebbles, sand, silt, & clay
2. Chemical Sedimentary: Form when minerals ppt out from a solution- like when seas or lakes evaporate
a) Limestone: calcium carbonate (found in ocean waters) comes out of solution (crystals grow together) & are
deposited on sea or ocean floors.
b) Rock salt: lakes or seas evaporate; deposit the mineral halite; when mixed w/other minerals will form halite rock.
3. Organic: Formed from the remains of once living things or from life processes (therefore not WHAT??)
Fossils are the main organic material from both plants & animals
How Sediments Travel
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Particles are transported by wind & water & glaciers. Water moves the greatest amount of sediments.
Stream Transport:
Particles will become rounded & smooth as they bang & rub against each other= abrasion
The > the distance traveled, the smoother & rounder the particles become
The > the velocity of a stream, the > the particles they can transport
3. Deposition of Sediment occurs when a stream slows down…
a) Enters a standing body of H2O
b) When the gradient decreases
4. Deposition by a stream results in sorting of sediments= graded deposit
a) The largest particles will be deposited 1st – as the velocity decreases more, the smaller particles will be deposited
further out into the body of H2O
Useful Sedimentary Rocks
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Minerals, corals, & snails make the shells from the mineral calcite. When they die, shells accumulate on the ocean
floor.
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If the shell fragments are large, they’re called coquina 
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If the shell fragments are microscopic, they’re called chalk
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Coal: forms when pieces of dead plants are burned under other sediments in swamps & changed by
microorganisms.
V. Metamorphic Rock
Origin: rocks that change due to an increase in To & pressure or undergo changes in composition are called
metamorphic rocks.
These can also change from igneous, sedimentary, or other metamorphic rocks.
A. Heat & Pressure:
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rocks beneath the earth’s surface are under great pressure from overlying rock layers. Once heat & pressure hit a
certain point it’ll turn to magma
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If the heat isn’t enough to cause melting, minerals will flatten out like a pancake (will show type of layering).
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Any type of rock can become metamorphic
Eg: granite (igneous)  gneiss (metamorphic)
Eg: addition of pressure:
shale  slate  phyllite  schist  gneiss
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Met rocks are NOT porous
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They’re easy to split, have thin layers of alternating materials called banding, & are similar to the parent rock.
B. Classification: again, metamorphic rocks are formed from any of the 3 types of rocks due to heat & pressure.
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They can be classified by their texture: Foliated or Non-foliated
B. Classification
1. Foliated: when mineral grains flatten & line up in parallel bands, the met. rock has a foliated texture. Eg: Slate &
gneiss
2. 2. Non Foliated: in some met. rocks, no banding occurs; the mineral grains change, grow, & rearrange, but do
NOT form bands. Eg: marble
C. Types of Metamorphism
 Contact- caused by igneous activity
 Dynamic - aka cataclastic; associated with faults & earthquake zones
 Regional- caused by tremendous pressures; associated with tectonic plate activity
1. Contact Metamorphism
Igneous Intrusions
• size and type of magma important - mafic magma hotter than felsic
• Heat decreases away from magma
• forms a zone of altered country rocks called - Aureoles
• Sometimes creates a metamorphic rock called a hornfels -in essence a “cooked” rock
2.
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Dynamic Metamorphism aka Cataclastic Metamorphism
associated with Fault Zones
Places where the Earth's crust ruptured
Rock pulverized
heat and pressure come from movement along the fault
resultant rock is known as a Mylonite
3. Regional Metamorphis
 Most common form of metamorphism
 caused by large scale forces - lithospheric plate collision covers very large areas metamorphic belts or zones
 Zones are characterized by - Index Minerals that form under specific temperatures and
pressuresmetamorphic facies: The metamorphic facies are groups of Index Minerals compositions by
which it can be recognized commonly associated with shields: stable areas of crystalline rocks
Metamorphic Zones