Earth ScienceEarth ScienceUnit 1Unit 1Chapter 3Chapter 3

Lesson 2Lesson 2

Sedimentary RocksSedimentary Rocks

SedimentsSediments

• Defined: Particles of minerals, rock fragments, shells, leaves, bones, and fragments of other once living things

Sedimentary RocksSedimentary Rocks

• Defined: rocks that form from sediments that are compressed and cemented together– The process of creating sedimentary rocks is

known as Lithification

How are they Formed?How are they Formed?

• Step 1: Compaction- pressure pushes sediments together, leaving little space between them

• Step 2: Cementation- water carries dissolved minerals through the sediments and leaves them in the open spaces

How are they Classified?How are they Classified?

• They are classified by the way they form– Clastic Rocks- Made from separate rock

particles and fragments that were eroded away from older rocks

• Examples: Sandstone, Shale

Classification Continued…Classification Continued…

• Congiomerate rock- A rock composed of rounded, pebble-sized rock fragments– They form where sediments are deposited– Example: mouths of rivers and beaches– Breccla- a Type of congiomerate rock

composed of sharp cornered fragment

SandstoneSandstone

• Defined: A clastic rock composed of rounded sand sized grains– Contains quartz– Very porous, so water can move easily

through it

ShaleShale

• Defined: A clastic rock composed of clay-sized particles in flat layers– Layers a brittle and easily broken– The most common sedimentary rock

Chemical Sedimentary RocksChemical Sedimentary Rocks

• Composed of minerals that were once dissolved in water– Formed after water evaporates– Rock salt and gypsum are two examples

Organic Sedimentary RocksOrganic Sedimentary Rocks

• Rocks made from the organic material of decaying organisms – Coal is an example

Questions to AnswerQuestions to Answer

• What is an example of how chemical sedimentary rocks are formed?