Unit 3: Lesson 3: Sedimentary Rocks Assessment, p. 79

Which type of sediments do you think would undergo more compaction-grains of sand or grains of clay?

Because they are smaller, clay particles undergo more compaction than sand-size particles.

Where do the cements that hold sediments together come from?

Cements are dissolved minerals that are deposited in the tiny places among the sediments.

What is compaction?

Compaction is the process that squeezes, or compacts, sediments.

Name four clastic sedimentary rocks and explain how these rocks form.

Conglomerate, breccia, sandstone, shale, and siltstone are clastic rocks. Clastic rocks form when bits of weathered materials are compacted and cemented together.

Explain how three different features of sedimentary rocks can be used to determine how, where, and when the rocks formed.

Each layer of sedimentary rock records a period of deposition. Ripple marks indicate that a rock bed formed in water. Mud cracks are indicative of unusually dry periods. Fossils can be used to determine if a rock formed on land or in the ocean, if the climate was hot or cold, or rainy or dry, and when the rock containing them formed.

Name four chemical sedimentary rocks and explain how these rocks form.

Most limestones, rock salt, rock gypsum, flint, and chert are chemical sedimentary rocks that form when dissolved minerals precipitate from water.

Suppose you found a sedimentary rock in which ripple marks were pointing toward the ground. What could you conclude about the rock.

Ripple marks indicate that a rock formed in water. And, because the ripple marks were pointing down, one can infer that the rock has been overturned from its original position.

Contrast weathering, erosion, and deposition.

Weathering is any process in which rocks are broken down into smaller pieces. Erosion involves the weathering and removal of sediments. Deposition is the dropping of sediments by agents of erosion.