What are the two main processes that turn loose sediment into solid sedimentary rock?
AMelting and cooling
BCompaction and cementation
CEvaporation and condensation
DHeating and pressure until the rock melts
Compaction squeezes the sediment grains closer together under the weight of layers above. Cementation happens when dissolved minerals fill the spaces between grains and act like glue. Together, these processes turn loose sediment into solid rock. Melting would produce igneous rock, not sedimentary.
Question 2 Short Answer
Why are fossils most commonly found in sedimentary rocks rather than igneous or metamorphic rocks?
Think about your answer, then reveal below.
Model answer: Sedimentary rocks form from layers of material that accumulate gently, so organisms that die and get buried can be preserved. Igneous rocks form from melted rock that would destroy any remains, and metamorphic rocks form under heat and pressure that would crush or distort fossils.
The gentle, layer-by-layer formation of sedimentary rocks is ideal for preserving plant and animal remains. The extreme conditions that create igneous and metamorphic rocks would typically destroy organic material.
Question 3 True / False
Most sedimentary rocks are made from pieces of other rocks that were broken down by weathering.
TTrue
FFalse
Answer: False
While many sedimentary rocks (like sandstone and shale) are made from rock fragments, others form differently. Limestone often forms from the accumulated shells and skeletons of marine organisms. Rock salt forms when water evaporates and leaves mineral crystals behind. These are called biochemical and chemical sedimentary rocks.