lesson 2: rocks & minerals · 2019-04-30 · types of sedimentary rocks • inorganically...
TRANSCRIPT
Rock Classification
1) Igneous
2) Sedimentary
3) Metamorphic
**Classifications are based on formation
( how the rocks are made or formed).
• Form as molten rocks (magma or lava) cool.
• Lava – molten rock on Earth’s Surface
•Magma – molten rock inside the Earth
Igneous Classification
• Mineral composition (what it is made of)
• Texture = crystal sizes*Crystal sizes depend on _______________.Longer the cooling → the bigger the crystals!
• ESRT pg 6
Cooling Rate
Sedimentary Rocks Form from:
• Weathering & Erosion
• Sediments are deposited in watery environments
Types of sedimentary rocks
• Inorganically formed-• sediments compacted, cemented together
• Organically formed- from dead plant material – coal
• Chemically formed • Evaporates – formed from evaporation of sea
water • Limestone- compacted and cemented seashells
• Key notes: • Sedimentary rocks are the only rock group that
contains fossils!!!!!!!! • This is because sedimentary rocks that forms in
watery environments bury organisms QUICKLY preserving their skeletons
• There is no heat or pressure to destroy their remains
Salt mining on Bonneville Salt Flats, Utah.
Topic: Metamorphic Rocks
Type of Metamorphism
1) Regional: Caused by extreme pressure and heat.
2) Contact: caused by extreme heat. (shown by hachured lines)
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FQ: What rock type are metamorphic rocks formed from?
• Sedimentary
• Igneous
• Metamorphic
Any rock group can form
turn into another type
under the right conditions!
Evidence for plate tectonics
• The idea of plate tectonics was not recognized by the scientific community until the 20th century
• Can you imagine something as large as the continent of Africa Moving? How is this possible? What evidence do you think scientist have that proves this idea?
Continental vs. Oceanic • Result: Subducting oceanic crust
• Features:
1) Deep Sea Trench
2) Volcanoes & Mountains on continental crust
3) Earthquakes
Example: Cascade Mts., West USA
Oceanic vs. Oceanic • Result: Subducting oceanic crust
• Features:
1) Deep Sea Trench
2) Volcanoes Island Arc
3) Earthquakes
Example: Mariania Islands, Pacific Ocean
Continental crust vs. Continental crust
http://www.pbs.org/wnet/savageearth/animations/rift-collide.html
Diverging Plates • Result: Magma rises to surface, new crust forms
• Features:
1) Mid-Ocean Ridges
2) Rift Valleys
3) Earthquakes
4) Volcanoes
Example: Mid-Atlantic Ridge
Major Concepts
• The lithosphere is divided into 6 major plates• Pacific, American, Indian, African, Eurasian, Antarctic
• There are also many smaller plates as well
• Earthquakes result as the result of shifting plates- can occur at any type of plate boundary
• Volcanoes are also indicators of plate boundaries- although they may occur in the middle of a plate boundary – HOT SPOT –HAWAII
• Weathering
breaking rocks into smaller pieces called sediments
• Erosion
Moving rocks from one place to another
• Deposition
placement of sediments when they STOP moving
Topic: Physical (Mechanical) Weathering• Breaking rocks into smaller pieces without
chemical change.
1) Frost Action
Temp. drops, water
freezes & expands
Freezing &
thawing repeats
Frost action occurs mainly in Mid-latitudes (45oN or S)due to temperature change
Changes in sediments -
Abrasion:
• Sediments come in contact with other sediments
• Rocks become
smaller, rounder, and/or smoother
due to abrasion
Powerful Solutions:
Acid RainH2O (rain) + CO2 (carbon dioxide) = H2CO3 (carbonic acid)
Result:
*Dissolves limestone, calcite, and marble rock
*Underground cave systems
• Sinkhole Tour in Florida by CNN
• http://abcnews.go.com/WNT/video/sinkhole-strike-back-26846775
Environments of erosion and deposition
• Rocks become weather ( chemically or physically) and becomes sediments
• What happens to these sediments on Earth’s surface? Where do they go?
• Erosion = the transportation of weathered sediments
• Deposition = the placement of weathered sediments
A. Mainly in arid (dry) regions – little vegetation
B. Carries only small sediments
Wind erosion mainly occurs:
Erosion by streams
** V-shaped valleys – formed from Streams and Rivers **
Taughannock Falls in NY
Glacier• Naturally-formed mass of ice & snow that
moves under gravity’s influence.
• http://swisseduc.ch/glaciers/aletsch-livecam/index-en.html