Unit Three - Rocks and Minerals - Sedimentary Rocks Flashcards
How is a Sedimentary rock formed?
(Lithification)
A sedimentary rock is formed from the accumulation of sediment that is derived from preexisting rocks and other organic materials.
Accumalation - the gradual gathering of
Texture
When it comes to sedimentary rocks
The size, form and orientation of the CLASTS of a rock
Texture is the main factor of sedimentary rock identificication
What are Clastic Sedimentary Rocks?
Those that are formed from rock particles or other fragments that become compressed and glued together.
The texture that identifies the type of rock.
What are Crystalline Sedimentary Rocks?
Those that formed from some chemical action in water such as precipitation and evaporation. Those mineral grains “fall out” and later forms into a sedimentary rock.
Ex: When a seawater lake evaporates, the salt that is left behind and overtime will form into rock salt.
Ex: Halite or Salt
Bioclastic
Rocks that FORMS from the remains of plants and animals
What are the three types of sedimentary rocks?
Bioclastic
Clastic
Crystalline
What are three ways that a sedimentary rock forms
Under bodies of water
- Cementation
- Compactation
- Chemical Action
What is cementation?
Sedimentary Rocks
Often when clasts such as clays, sand and silts are glued togehter.
Occurs as water between sediments dissolves and the *remaining material hold the clasts together. *
What is compaction
A reduction of volume in sedimentary layers due to the increasing weight of overlying sediemnts
(Rocks lose pore space and becomes tightly packed)
Chemical Action
A rock formed when dissolved minerals in water form a crystalline mass of fine crystals after evaporation
What are characteristics that that help identify sedimentary rocks?
- Horizontal Layers
- Forms at or near Earth’s surface where weathering can break down rocks into pieces
- Fossils
