Sedimentary Rocks (L8)

Question 1

What are sedimentary rocks?

Answer 1

rocks that are formed by the accumulation and hardening of sediment

Question 2

The 3 kinds of sediment and its quick definitions?

Answer 2

Clastic - consists of particles derived from pre-existing rocks (e.g., sand)

Chemical Sediment - Consisting of mineral matter precipitated from a solution (e.g., salt)

Biochemical Sediment - which consists of materials produced by organisms (e.g., shells)

Question 3

When exposed to earth’s surface, rocks are broken down by ____

Answer 3

processes of weathering (due to physical and/or chemical breakdown)

Question 4

Mechanical/physical weathering and how is it accomplished in nature?

Answer 4

involves the physical breakup or disintegration of rocks into smaller particles without changes in their composition

by physical agents (e.g, water, wind) but also can be aided by biological factors

Question 5

Chemical Weathering?

Answer 5

breakdown or decomposition of minerals due to chemical reactions of minerals with water or gases in the air

Question 6

what does the resistiance to weathering follow?

Answer 6

the same trend as the order of crystalization in Bowen’s Reaction Series

Question 7

Which temperature minerals are most stable at Earth’s surface and why?

Answer 7

Low-temperature minerals b/c Earth’s surface is a lot cooler than environments in which minerals form from magma

Question 8

When is Chemical weathering most intense?

Answer 8

in warm and humid climates

Question 9

What does chemical weathering produce and how?

Answer 9

residual products and free ions

Solid components are left as a residue and the remaining material is dissolved in water, in the form of ions

Question 10

Residual sedimentary particles can be dislodged and transported away in which 4 ways?

Answer 10

Gravity (mudflows, debris flows etc.)

Water (streams)

Wind

Glaciers

Question 11

The difference between weathering and erosion?

Answer 11

weathering is the breakdown of material whereas erosion involves the removal of material from the site of weathering

can act hand-in-hand but not same thing

Question 12

When do sedimentary particles ultimately come to rest?

Answer 12

once the transporting medium can no longer carry them

Question 13

what is the general rule of sedimentary particles being deposited?

Answer 13

smaller/lighter particles are deposited in less-agitated conditions than larger/heavier particles when transported by wind or water

Question 14

How do sedimentary particles experience some degree of sorting?

Answer 14

can be due to constant wave action, while the sand-sized particles settle out, finer grained particles are swept away

Question 15

What kind of transportation method of sedimentary particles results in poor assortment and why?

Answer 15

rapid transportation by events such as debris flows b/c particles aren’t remobilized and redeposited by sorting processes like waves

Question 16

How can geologists know the method in which the sediment was deposited by just looking at it?

Answer 16

b/c the characteristics of the clastic sedimentary rocks like fossils can provide info on where it was deposited

Ex., Shale is like rock and you can see microscopic clay particles that show fossils

Question 17

Lithification?

Answer 17

the transformation where once buried, sediment undergoes changes that transform it into rock

Question 18

How does Lithification work?

Answer 18

as sediment layers are buried to deeper and deeper levels under successive sediment layers, the particles are squeezed together as the spaces between them decrease in size

Question 19

What are the 3 stages of Lithification?

Answer 19

Deposition - where clasts are dropped or settled out

Compaction - as it gets buried under more sediments, the particles are closer together

Cementation - groundwater moves between the grains and the minerals it leaves behind glues the particles together

Question 20

How are clastic sedimentary rocks classified?

Answer 20

by grain size (clast size)

Question 21

Rock equivalent of gravel

Answer 21

Conglomerate (large clasts rounded if larger clasts angular = breccia)

Question 22

Rock equivalent of sand

Answer 22

sandstone (sand-sized particles, sandpaper feel)

Question 23

Rock equivalent of mud

Answer 23

Shale - if it breaks easily into small plates

Mudstone - if its more massive without a fine structure

Question 24

Equivalent of clay and sand?

Answer 24

Silt (particles barely visible under magnification)

Question 25

What does water on Earth’s surface all contain?

Answer 25

dissolved ions derived from weathered minerals and volcanic gases

Question 26

Why is the sea salty?

Answer 26

the proportion of positive ions of sodium and negative ions of chloride = halite (our common salt)

Question 27

What happens in sea water due to evaporation?

Answer 27

dissolved ions become so concentrated that the water cannot hold it so the ions join together and become minerals

Question 28

Evaporative deposits/minerals ?

Answer 28

when the water highly concentrated in sat cannot escape back to ocean and become further concentrated to the point that they become this

Question 29

2 common minerals in evaporative deposits are:

Answer 29

gypsum (clacium sulphate) and Halite (sodium chloride)

Question 30

Rock salt

Answer 30

a rock formed exclusively of halite (spread on our roads as de-icer)

Question 31

Rock Gypsum

Answer 31

a rock formed exclusively of gypsum (chalkboard chalk)

Question 32

What is Travertine?

Answer 32

the type of limestone which is a chemical limestone that forms in caves and hot springs (stalactites)

Question 33

What does biochemical sediment consist of?

Answer 33

materials that are produced by chemical processes associated with bio activity (shells, bones, teeth, etc)

Question 34

What are 4 common rocks that are formed from biochemical sediment?

Answer 34

fossiliferous limestone
reef limestone
chert
coal

Question 35

Fossiliferous Limestone

Answer 35

type of biochemical limestone composed entirely of calcite shells (skeletons) of organisms

Question 36

Chalk

Answer 36

a variety of fossiliferous limestone, made of microscopic skeletons of plantonic algae

Question 37

Chert

Answer 37

the solidification of the common biochemical sedimentary rock where the silica of an organism’s skeleton dissolves and forms a gel on the seafloor

Question 38

Why was Chert used for its arrowheads and tools?

Answer 38

due to its hardness and the sharp cutting edge from its conchoidal fractrure

Question 39

Coal

Answer 39

a special type of biochemical sedimentary rock that is largely composed of organic matter from plants

Question 40

What is interesting about coal?

Answer 40

it’s one of the few rock types that doesn’t necessarily contain any minerals

Question 41

Where are sedimentary rocks also widely used in?

Answer 41

Construction of buildings

Question 42

What is the NSB and GSB made of?

Answer 42

Whirlpool Sandstone (100% quartz sand)

Question 43

Where does Tyndall Stone get its attractiveness from?

Answer 43

the dark colored mottled shapes against a lighter tan-colored background

Question 44

What is a Dolostone?

Answer 44

much like limestone but is composed of mineral dolomite instead of calcite

Question 45

Why is the dolostone “Eramosa Limestone” ideal for flagstones?

Answer 45

b/c its naturally finely laminated and easily splits into flat slabs