Sedimentary Rocks Flashcards
How are Sedimentary Rocks formed?
They form in layers known as strata, and are made from sediments that have been cemented or compressed together.
Examples of Sedimentary Rocks include… (name one?)
Gypsum, shale, limestone
Types of Sedimentary Rocks (the names of these change depending on what teacher you have)
Clastic, Chemical, Biochemical/Organic
How are Sedimentary Clastic Rocks made?
Made of pre-existing rocks (e.g. shale)
How are Sedimentary Chemical Rocks made?
Precipitated from a solution, such as saltwater. (this solution already contains minerals, so as it precipitates and the water leaves, it becomes rock.)
How are Sedimentary Biochemical/Organic rocks made?
Made from the remains of dead organisms, for example, limestone. (these dead organisms leave behind biological matter that over many years is compressed into coal)
What is a fossil?
Fossils are preserved evidence of organisms that once existed.
Fossil Types
Mould
Cast
Trace
True Form
Can you name a way fossils form?
Unaltered Preservation
(most common) Premineralisation/Petrification
Replacement
Carbonisation/Coalification
Recrystalisation
What is the Law of Superposition?
The law of superposition states that in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest layer is on the bottom. Each layer being younger than the one beneath it and older than the one above it.
(Basically, youngest layer on top, oldest on the bottom)
What are conglomerate rocks?
Sedimentary rocks mainly found in riverbeds with large, coarse rounded grains.
Why can you not find fossils in igneous and metamorphic rocks?
Igneous rocks undergo great heat and metamorphic rocks also undergo extreme heat or pressure - fossils cannot usually survive these conditions.
