Download Sedimentary Rocks

SEDIMENTARY ROCKS
FORMATION…
• All sedimentary rocks form from the compaction
and cementation of sediments
• Sediments are small pieces of rocks and shells that
have been transported and deposited by water,
wind, gravity or ice (glaciers)
IMPORTANT PROCESSES….
•Weathering: breakdown of rocks at the Earth’s
surface
•Erosion: transportation of sediments to new
locations
•Deposition: sediments are laid down/dropped
in a layer
IMPORTANT PROCESSES….
• Compaction: happens when sediments are deeply buried;
weight and pressure of overlying sediments squeezes out air
& water and presses sediments tightly together
• Cementation: takes place when dissolved minerals are
deposited in the tiny spaces among the sediments; acting like
glue or cement to turn loose sediment into solid rock
• Common cementing minerals: calcite, silica, iron oxides, clay
minerals
• The combination of theses two processes together is called
lithification
CLASSIFICATION OF SEDIMENTARY ROCKS….
• Sedimentary rocks are divided into two categories:
• 1) Clastic: composed of weathered bits of rocks, minerals, or
shells
• Classified by particle size
• Includes shale (most abundant), sandstone, conglomerate
CLASSIFICATION OF SEDIMENTARY ROCKS….
• Sedimentary rocks are divided into two categories:
• 2) Non-Clastic
• A. Chemical: form when dissolved substances precipitate,
or separate from water (through evaporation or
precipitation)
• Includes chert, flint, agate, halite, gypsum
• B. Organic: Formed from dead plant material, shells, and
skeletal material made by living things that have been
buried and compressed.
• Includes limestone, coal
HOW TO KNOW….
• How to know if your looking at sedimentary rock…
• In addition to noticing larger pieces of rock or shell, seeing
the textures such as
• Ripple marks indicate water once flowed
• Mud cracks form when saturated mud dries out.
• Fossils from the remains of plant and animals
**these would all be destroyed by the processes that
form igneous and metamorphic rock.