Unit 1: Interpreting Geologic History Flashcards
(17 cards)
1
Q
Sedimentary rock
A
- Formed from fragments of material (sand, shell, pebbles) called sediment
- Sediment accumulates into layers and hardens into rock
- Usually the only type to contain fossils
- Examples: sandstone, limestone
2
Q
Metamorphic rock
A
- Formed under the surface of the Earth from intense heat/pressure (squeezing)
- Have ribbonlike layers or shiny crystals
- Examples: gneiss, marble
3
Q
Igneous rock
A
- Formed when magma cools and hardens (sometimes inside the Earth, sometimes from lava)
- With lava, it cools quickly and yields no crystals making it look shiny/glassy
- Bubbles = tiny holes/spaces
- Examples: basalt, obsidian
4
Q
Rock cycle
A
- Volcanic eruption
- Lava cools into igneous rock
- Igneous rock is weathered and turns into sediment
- Sediment accumulates and forms sedimentary rock (lithification)
- Sedimentary rock is pressured into metamorphic rock
- Metamorphic rock is melted into magma
- Magma builds up and leads to volcanic eruption
5
Q
Facies
A
observations, what characteristics a deposit has
6
Q
Depositional environment
A
The environment in which the rock was deposited
7
Q
Facies vs. Depositional environment
A
Facies = characteristics of the DEPOSIT
Depositional environment = characteristics of the ENVIRONMENT
8
Q
Color of rock
A
OXYGEN LEVEL
- Black = anoxic, some organic material
- Red = extremely oxygenated bc on land/exposed to air
- White = indicates shallow, well-oxygenated water
9
Q
Grain size
A
ENERGY of depositional environment
- Fine = high energy
- Coarse = low energy
10
Q
Shape
A
DISTANCE grains had to travel, distance from origin
11
Q
Types of bedding
A
- Parallel = no strong current
- Cross bedding = directional current
- Graded = intense pulses of sedimentation
12
Q
Thickness
A
TIME
- thin = short period of time
- thick = long
13
Q
Sedimentary structures
A
- mudcrack: wide on top, narrow at bottom. Forms as cracks in dry mud
- ripples: indicate directional current
- burrows: created by animals .’. O2/food availability
14
Q
Delta front
A
Transitional
- sandstone
- bi-directional cross bedding
- tree roots/shelled organisms
- Brackish
15
Q
Delta plain
A
Continental
- coals, sandstone, shale
- uni-directional cross bed
- swamps
- Fresh river
16
Q
Pro delta
A
Shallow marine
- shale
- parallel beds
- least amount of energy
- Salty marine
17
Q
Formation
A
A formation is a rock unit that is distinctive enough in appearance that a geologic mapper can tell it apart from the surrounding rock layers
