Transcript 3.3 Sedimentary Rocks

Today’s Objective:
What Makes Sedimentary Rocks Special?
Sedimentary
Rocks are one of the three
main rock types
A sedimentary rock can form one of
three ways:
1. by the deposition of the weathered
remains of other rocks
2. by the deposition of the results of
biologic activity
3. by precipitation from solution.
• Compaction – is a
process that squeezes,
or compacts,
sediments.
• Cementation – “glue” takes place when
dissolved minerals are
deposited in the tiny
spaces among
sediments.
• Weathering - is a process in which
rocks are physically and chemically
broken down by water, air, and living
things.
• Erosion - involves weathering and the
removal of rock.
• Deposition - when an agent of erosion
– water, wind, ice, or gravity – lose
energy, it drops the sediments.
Classification of Sedimentary Rocks
• Can be classified into two main groups
according to the way they form.
Inorganic Land Derived
(AKA) Clastic Sedimentary Rock composed of weathered bits of rocks
And minerals.
These rocks are classified by particle size.
EXAMPLES of Inorganic Land Derived
Conglomerate
Shale with
Plant Fossils
Large grain size
Small grain size
Chemical Sedimentary Rocks –
Forms when dissolved minerals
precipitate from water solutions.
(water usually evaporates or boils)
Ex: Limestone & rock salt.
Salt Flat
Organically Formed Sedimentary Rocks –
Forms when shell fragments are
cemented together or when plant remains are
compacted into rock.
• Ex: Fossiliferious Limestone & Bituminous Coal
Features only found in
Sedimentary Rocks
1. The Law of Superpositioning - In
undisturbed rocks, the oldest layers are
found on the bottom and the youngest at
the top.
2. Ripple Marks – rock formed along
the beach or stream bed.
3. Mud Cracks - formed when wet mud or
clay dried and shrank, leaving a rock
record of a dry environment.
4. Fossils – traces of remains
of ancient life.
Trilobite
Where is the oldest layer located
on this picture?