Sedimentary & Metamorphic Rocks Flashcards
How do sedimentary rocks form?
From the deposition (dropping) of sediment in different environments
What are the 2 primary types of sediment? Hint: Each is defined by its source
Clastic : From preexisting rock
Biogenic : From Life (Sea Critters)
How are clastic sediments formed? What’s their origin and where do they go?
Form from weathered rock
Clastic sediments form in the mountains and is ultimately transported to the ocean
What are mountains mostly dominated by and what does it do in the sedimentary rock cycle?
Large pieces of angular Gravel, from pebbles to boulders
Since mountains are steep-sided, these angular gravel pieces can go into the river
What do rivers primarily consist of and what does it do in the sedimentary rock cycle?
They consist primarily of rounded pebbles that are in the river, losing their corners
It makes the angular gravel from the mountains smoother into rounded pebbles which then travel into beaches
What do beaches primarily consist of and what does it do in the sedimentary rock cycle?
They consist primarily of sand grains that are carried to the coastline by flowing rivers
The rounded pebbles from the river will eventually become smaller and smaller due to breaking down as they travel through the river, which will lead to the ocean
What do deep oceans primarily consist of and what does it do in the sedimentary rock cycle?
The deep ocean consists of fine mud that drifts far out into the ocean and eventually sinks due to small sand grains from beaches
List the stages of the sedimentary rock cycle. (What type of rock and where)
1.) Angular rock (pebbles to boulders), Mountains
2.) Rounded pebbles, Rivers
3.) Sand, Beaches
4.) Mud (Fine mud), Deep Oceans
Mountains —>Rivers —>Beaches —>Deep Oceans
How does grain size vary? What happens as the sediment travels?
Grain size decreases with increasing transport due to physical breakage and rounding
Sediment becomes more rounded as it travels, the longer it travels, the rounder it will be
Where do deposits of clastic sediments appear?
They are typically thich around the edges of the continents
Southeastern United States by Golf of Mexico
Off the coast of northeastern South America
Off the coast of South Asia
How do rivers flow into oceans?
By flowing into river deltas, the river slows down when it hits the ocean and deposits the sediment that it’s carrying
Some examples of river deltas
Nile River Delta, Egypt
Mississippi Delta, Louisiana
What happens to sediment as it crosses the river deltas?
What is this specific action called?
Sediment is sorted as it crosses the delta
Sand is dropped close to the shore on the beach, while mud is carried out to the deep ocean
How are Clastic sedimentary rocks classified?
They are classified by grain size
What are some clastic sedimentary rocks and their type in regard to the sedimentary rock cycle?
Breccia, Angular Gravel
Conglomerate, Rounded Pebbles
Sandstone, Sand
Mudstone, Mud
Size of each particle for grain size
> 256 mm: Boulder
64-256 mm: Cobble
4-64 mm: Pebble
2-4 mm: Granule
1/16 - 2 mm: Sand
1/256 - 1/16 mm: Silt
<1/256 mm: Clay
What is another way of classifying sedimentary rocks besides grain size?
Also classified by texture and structure within their layers
Structures called sedimentary structures
What are the two types of sedimentary structures?
Horizontal bedding & Cross bedding
How does horizontal bedding form?
Form from the slow and steady rain of sediment to the seafloor
Just like an hourglass, oldest layers on the bottom while youngest layers on the top
How does cross-bedding form?
Forms as sand is pushed up one side of a sand dune and down the other
Sand layers are preserved as they tumble down
What is Mudstone?
Tends to be a dark colored rock that has tiny particles of mud <1/256 mm in size
This is where we typically find most of our fossils especially early fossils
What is GRAY Mudstone?
(Deep Ocean) Gray mudstone in particular forms in deep, quiet-water environments where wave activity is minimal
What is RED Mudstone?
(River on land) Red mudstone in particular forms in and around muddy rivers where iron in the mud is rapidly rusted
IMPORTANT : These mudstones often have land-based fossils
What is Sandstone?
Light-colored rock that consists of sand grains made primarily of quartz
Sometimes horizontal bedding, sometimes massive texture
Where does sandstone form from?
Forms on sandy beaches where waves crash away mud, leaving behind sand
Layered levels of sediment, it can go into the Earth and get heated up to high temperatures to form sandstone
What 2 primary environments do beaches consist of?
Surf Zone and Swash Zone
How can you tell where the surf zone and swash zone are?
Both are each marked by a distinctive sedimentary structure
SWASH ZONE: HORIZONTAL BEDDING
SURF ZONE: CROSS-BEDDING
Where is another place that sandstone can form besides the beaches?
Sandstone can also form in deserts where wind concentrates sand into giant sand dunes, which can create cross-bedding as tall as a house
What is one historical monument created with Sandstone?
The Abu Simbel Temple in Egypt carved out of sandstone with large-scale cross-bedding in it
What is Breccia?
Breccia consists of particles of gravel-sized sediment that are angular or sub-angular
Where does Breccia typically form?
Breccia forms from debris flows, flash floods, and landslides that operate very briefly
Minimal transport keeps these pieces very angular
What is Conglomerate and how does it form?
Conglomerate consists of gravel-sized sediment that is rounded to well-rounded
Typically formats in high-energy rivers where there is a local source of gravel
What are Biogenic sedimentary rocks?
Biogenic sedimentary rocks are sedimentary rocks that consist of biological remains
How do you classify Biogenic sedimentary rocks?
Biogenic sedimentary rocks are classified by its composition (chemistry)
What is limestone?
Any sedimentary rock that is composed of the mineral calcite
Calcite from limestone is from shells or anything that is calcite from dead animals, fossils are encased in limestone, and calcite mud is also formed
What is calcite mud?
Calcite mud comes primarily from algae
IMPORTANT: The algae Halimeda has a calcite skeleton that breaks down over time and releases calcite mud
What’s common in most other biogenic sediment?
Most other biogenic sediments consist of seashells and other noticeable sea critters
Nearly all seashells are made of calcite. T/F
TRUE
Where does limestone form? What do you call these places?
In tropical waters where there is little sediment input from continents EX. BAHAMAS
These isolated areas where there is little sediment are called carbonate platforms
If there are clastic sediments, then there are no carbonate platforms, no limestone
What is responsible for most of the microscopic biogenic sediment in the ocean? What are they called?
Microorganisms, most are photosynthetic single-celled algae
Coccolithophores : Calcite shells
Diatoms : Quartz shells
What is chalk and what is it made out of?
The name for limestone rocks that consist of the calcite microfossils of coccoliths
IT ACCUMULATES IN THE DEEP OCEAN
Example: White Cliffs of Dover in Southern England consists of chalk
What is diatomite? How does it differ from chalk?
Diatomite is the name for a similar powdery rock made from quartz fossils of diatoms instead of calcite
Can also accumulate deep in the ocean just like chalk
How does coal form?
Coal forms from the compaction of swamp plants that fail to decay under oxygen-poor waters
Progressive burial will release water and gases from the coal, increasing the carbon content and energy yield
Where does coal primarily form in?
Coal forms primarily in swamps where stagnant water loses its oxygen almost immediately
Oxygen is necessary to break down organic matter, no oxygen means that there will be a build-up of dead plants
What are the environments for each rock type listed?
Gray Mudstone
Red Mudstone
Bedded/Cross-Bedded Sandstone
Large-scale Cross-Bedded Sandstone
Breccia
Conglomerate
Limestone
Chalk
Diatomite
Coal
How does loose sediment such as sand or pebbles become a sedimentary rock of their respective rock type?
By a process known as Lithification
What is Lithification?
The process that transforms loose sediment into solid sedimentary rock
Pressure from the burial of loose sediment squeezes particles together
The formation of minerals from the compacted sediment cements the sediment together
What are the two steps of lithification?
COMPACTION AND CEMENTATION
What is the rock cycle?
The process by which one rock type is converted to another rock type
What rocks can make metamorphic rocks?
Both Igneous and Sedimentary rocks, through immense heat and pressure of Earth’s interior, as it gets close to the mantle
What is metamorphism?
Process that changes rocks in response to increases in temperature and pressure
What happens to the layers of sediment as it is being deposited in regard to pressure?
As layers of sediment are deposited, it will increase the pressure on the layers below, the deeper the burial the higher the pressure
Highest pressure at the bottom
What can enhance pressure for metamorphism?
The pressure can be enhanced due to subduction since marine sedimentary rocks that are subducted become buried deep below Earth’s surface
Where can metamorphic rocks form?
From plate boundaries since there are subduction points that create intense pressure and heat
What are the two groups of metamorphic rock?
Foliated Metamorphic rocks (Stripes)
Non-Foliated Metamorphic rocks (Non Stripes)
What creates the foliation in metamorphic rocks?
Foliation forms when minerals align perpendicular to the orientation of maximum stress
This redistributes the stress over a larger surface area of mineral grains
Stress focused on a small area is unstable
Stress focused on a larger area is stable
What is the parent rock for all foliated metamorphic rocks?
Foliated metamorphic rocks begin as mudstone and become more foliated with increasing metamorphism
The layering becomes progressively more developed
What is an important thing to note about foliation in regard to how it behaves?
Foliation in metamorphic rocks behaves completely independently of other rock structures
Foliation can be oriented perpendicular to bedding
What are all the types of rocks mudstone can turn into through increasing temperature and pressure?
IMPORTANT TO NOTE, GNIESS IS THE LAST ROCK THAT A METAMORPHIC ROCK CAN BE BEFORE IT TURNS BACK INTO MAGMA
What happens to mineral composition in metamorphic rocks with increasing temp and pressure?
Unstable minerals within the rock will recombine into new stable minerals, minerals are only stable at very specific temperatures
What are all the mineral composition with respect to increasing temp and pressure?
What is slate?
Resembles mudstone, but has foliation along which it tends to break into flat slabs
A SOUGHT AFTER BUILDING STONE
What is Phylite?
Metamorphic grade above slate and has a silvery yellow satin like shine
What is Schist?
Strong foliation and typically sparks, grade above phyllite and is well known for having red garnets
What is Gneiss
Has the strongest foliation, consisting of layers of light and dark elongated mineral grains
What is quartzite commonly used for compared to marble?
Building but not for sculpting while marble is great for sculpting mad at building
What are the 2 primary types of NON FOLIATED ROCKS that are common on Earth?
MARBLE AND QUARTZITE
What’s the difference between marble and quartzite?
Marble forms from the metamorphism of limestone (limestone has calcite)
Quartzite forms from the metamorphism of sandstone since sandstone typically consists of the mineral quartz
What do non-foliated rocks undergo in regard to temp?
Non-foliated rocks undergo recrystallization in response to increasing temp
How do non foliated rocks form?
They form from contact metamorphism, occurs when sedimentary rocks get heated and cooked by a shallow magma body
What is recrystalization?
Crystals grow in size during metamorphism and form a mosaic, like a stained glass window
How do foliated rocks form?
They form from burial metamorphism when rocks are buried deep in the ground
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