Ch. 6. 3 - Sedimentary Rock

Where do the sediments that form clastic sedimentary rock come from?

other rocks

organic sedimentary rock

sedimentary rock that forms from the remains of plants or animals

clastic sedimentary rock

sedimentary rock that forms when fragments of preexisting rocks are compacted or cemented together

chemical sedimentary rock

sedimentary rock that forms when minerals precipitate from a solution or settle from a suspension

List the seven features that sedimentary rocks can have.

stratification, cross-beds, graded beds, ripple marks, mud cracks, fossils, concretions

What causes chemical sedimentary rocks to form?

the evaporation of water

cementation

the process in which minerals precipitate into pore spaces between sediment grains and bind sediments together to form rock

compaction

the process in which the volume and porosity of a sediment is decreased by the weight of overlying sediments as a result of burial beneath other sediments

What type of water can drop poorly sorted sediment?

water that slows quickly

Which structure are you more likely to find in an organic sedimentary rock, mud cracks or fossils? Explain your answer.

An organic sedimentary rock is more likely to contain fossils than mud cracks. Fossils are signs that living things once existed. Organic sedimentary rocks form from the remains of living things, so they are likely to contain fossils. Mud cracks form when mud dries and shrinks. Organic sedimentary rocks generally do not form from mud, so mud cracks are unlikely to appear.

What causes mud to crack as it dries?

As it dries, it shrinks.

How is compaction different from cementation?

Compaction causes sediment particles to move closer together. Cementation causes sediment particles to stick to one another.

What happens during compaction?

Pressure on sediment squeezes the particles closer together.

A clastic sedimentary rock is made up of smooth, round sediment pieces that are all about the same size. What can you infer about how the sediment that formed the rock was transported and deposited?

The particles are all about the same size, so they are well sorted. Well-sorted sediment can be laid down by water that slows gradually, so the sediment in the rock may have been deposited by that type of water. In general, sediment particles become smoother and rounder as they are transported, so the sediment was probably transported far from its source.

What is the main difference between well-sorted sediment and poorly sorted sediment?

The particles in well-sorted sediment are all about the same size. Those in poorly sorted sediment are many different sizes.

A scientist is studying a sedimentary rock that did not form through compaction and cementation. What kind of sedimentary rock is the scientist studying? Explain your answer.

The scientist is studying a chemical sedimentary rock. These rocks form when water evaporates, not through compaction and cementation.

Some kinds of limestone form when calcium carbonate crystallizes from shallow ocean water. Are these limestones chemical sedimentary rocks or organic sedimentary rocks?

chemical sedimentary rocks

What causes a sediment particle to become smoother and rounder over time?

collisions with other particles or with other objects

What is stratification?

layering in a sedimentary rock