EOSC 210 Midterm 1 Exam Questions with All Correct Answers 2024/2025 Latest Update
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EOSC 210
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EOSC 210
EOSC 210 Midterm 1 Exam Questions with All Correct Answers 2024/2025 Latest Update
What are the main sedimentary rock types? - Answer- 1. Clastic - clasts are fragments or particles of weathered and eroded rocks (eg. sandstone)
2. Chemical (evaporites) - formed through precipitation (eg. halit...
EOSC 210 Midterm 1 Exam Questions
with All Correct Answers 2024/2025
Latest Update
What are the main sedimentary rock types? - Answer- 1. Clastic - clasts are fragments
or particles of weathered and eroded rocks (eg. sandstone)
2. Chemical (evaporites) - formed through precipitation (eg. halite, gypsum)
3. Organic (eg. chalk, limestones, coal)
How are clastic sedimentary rocks transported? - Answer- 1. transported as suspended
load with dissolved load (ions) and bed load
2. as they get larger, particles will either settle or slowly move along the bottom of the
lake through other processes (eg. traction, saltation, or rolling)
How can we tell if a sedimentary rock has been transported a further distance? -
Answer- sediments get more rounded, finer grained, and well sorted the further away
from the source rock they are
What's considered a mudrock? - Answer- >75% silt and clay, not bedded if mudstone
>75% silt and clay, thinly bedded if shale
more silt than clay, siltstone
What's considered a sandstone? - Answer- dominated by sand, >90% quartz - quartz
sandstone
dominated by sand, >10% feldspare - arkose - pink colored
dominated by sand, >10% rock fragments, >15% silt and clay - lithic wacke
What's a conglomerate? - Answer- pebbles to boulders in a finer grained matrix,
rounded clasts
What's a breccia? - Answer- pebbles to boulders in a finer grained matrix, angular clasts
What is tufa? - Answer- CaCO3, precipitated from cold springs, similar to Travertine
(CaCO3), which is precipiated from hotsprings
What are Speleothems? - Answer- precipitated in caves AKA Stalagmites (CaCO3)
Where's the most famous example of chemical sedimentary rocks (evaporites)? Think
europe! - Answer- 6 million years ago, the African and Eurasian plates closed the
, straight of Gibraltar, drying up the Mediterranean Sea, and forming evaporites (eg.
Dead Sea)
How is coal formed? What is coalification? - Answer- formed from plant remains, in
areas with lots of decaying plant matter (bogs, swamps), vegetation is buried by other
vegetation and mud and turns to peat, peat lithifies into coal
Coalification: conversion of peat to sedimentary rock under pressure and temperature
What is a sedimentary bed? Bedding Plane? Formation? - Answer- a layer of sediment
or sedimentary rock with a recognizable top and bottom
bedding plane = the boundary between 2 beds
series of beds = formation
What are the two different types of ripples formed in sand? What do they tell us? -
Answer- ripples tell us if someone is a river, desert or a beach
- deserts and rivers have asymmetric waves, whereas beaches have symmetric ripples
on both sides
What is a facies? - Answer- a distinct rock unit that forms under certain conditions of
sedimentation, reflecting a particular process or environment - vertical and lateral
differences reflect changes in conditions over time and space
What is Walther's Law? - Answer- a vertical sequence of facies reflects lateral changes
in a depositional environment
- when depositional environments migrates, sediments of one depositional environment
come to lie on top of another
What is a marine transgression? - Answer- sea level rises relative to land surface,
depositional enviornments migrate towards land, marine sediments deposited on top of
continental sediments
What is a marine regression? - Answer- sea level falls relative to land surfaces,
depositional environments migrate towards the sea, continental sediments deposited on
top of marine sediments
Why are sedimentary rocks important for the oil and gas industry? How do oil and gas
form? - Answer- They contain lots of petroleum (from organic rock sediments that settle
to the ocean floor) - ideal conditions for accumulation of organic material includes a
stagnant ocean floor with little oxygen
source rocks: shale, or any organic-rich rock, these rocks are buried until around 60
degrees C, when oil begins to form
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