Zusammenfassung der Ressource
Unit 8.3-Sedimentary Rocks
- Clastic
- Clastic Sedimentary Rocks are formed when sediments are laid
down by wind and water,gravity & ice, and then compacted and
cemented.
- They contain broken pieces of
rocks. These pieces are known
as clasts
- They may have layers like stacks of pages in a
book because the sediments build up one on
top of another as they are deposited.
- These may contain rock
fossils
- Chemical
- When minerals dissolved in groundwater
crystalline within the sediments or when the
water evaporates
- Chemical sedimentary
rocks are quite soft.
- This helps to distinguish them
from much harder igneous rocks
- Biogenic
- Formed when dead plants or matter accumulate
- And then cemented
together
- These sediments are mostly from organisms but
they are may be small amounts of sediments from
weathered rock
- Coal is a type of
biogenic rock.
- Relative age of Rock Strata
- Relative age is not the actual age of the rock but only
indictaeds whether a rock is older or younger than
another rock.
- Be found over a widespread area
- Have lived in a narrow period of
time in the past
- have been abundant with lots of organisms