Formed from Formed from sediments.sediments.

SedimentsSediments - rock - rock fragments, mineral fragments, mineral grains, or animal & grains, or animal & plant remains.plant remains.

These sediments are moved by wind, These sediments are moved by wind, water, ice or gravity.water, ice or gravity.

Sedimentary rocks represent Sedimentary rocks represent 7%7% of of the Earth’s crust, but they cover the Earth’s crust, but they cover 70%70% of the Earth’s surface. of the Earth’s surface.

Sedimentary rocks are Sedimentary rocks are fossilfossil--carrying rocks.carrying rocks.

What turns sediments into solid What turns sediments into solid rock?rock?

LithificationLithification – process of – process of turning loose sediments turning loose sediments into solid sedimentary into solid sedimentary rocks.rocks.

What turns sediments into solid rock?What turns sediments into solid rock?

Water or wind Water or wind breaks downbreaks down and and depositsdeposits sediment (erosion & sediment (erosion & deposition)deposition)

CompactionCompaction

As sediment builds up, the weight of As sediment builds up, the weight of overlying material compresses overlying material compresses deeper sediments.deeper sediments.

The deeper a sediment is buried, the The deeper a sediment is buried, the more it is compacted and the firmer more it is compacted and the firmer it becomes.it becomes.

CementationCementation - Dissolved minerals - Dissolved minerals flow between the particles and flow between the particles and cementcement them together. them together.

How can sedimentary layers help us How can sedimentary layers help us understand the age of fossils?understand the age of fossils?

As sedimentary As sedimentary rocks are rocks are deposited, they deposited, they form horizontal form horizontal layers.layers.

Scientists know Scientists know that the layers on that the layers on toptop (and the (and the fossils in the top fossils in the top layer) are layer) are YOUNGERYOUNGER than than the fossils in lower the fossils in lower layers.layers.

3 Types of Sedimentary Rocks3 Types of Sedimentary Rocks

1.1. DetrialDetrial

2.2. OrganicOrganic

3.3. ChemicalChemical

3 Types of Sedimentary 3 Types of Sedimentary Rocks:Rocks:

DetrialDetrial (also called clastic)—made of (also called clastic)—made of brokenbroken pieces of other rocks. pieces of other rocks.

ExamplesExamplesShale, Sandstone, Shale, Sandstone, Conglomerate, and Conglomerate, and

BrecciaBreccia

OrganicOrganic—remains of —remains of plants and plants and animalsanimals are deposited in thick layers. are deposited in thick layers.

Ex. Fossil rich limestone is made from Ex. Fossil rich limestone is made from the shells of ocean animals; used to the shells of ocean animals; used to make chalkmake chalk

3 Types of Sedimentary 3 Types of Sedimentary Rocks:Rocks:

ChemicalChemical——mineralsminerals dissolved dissolved in lakes, seas, or underground in lakes, seas, or underground water.water.

3 Types of Sedimentary 3 Types of Sedimentary Rocks:Rocks:

Mineral crystals are made as the shallow water that has flooded the bottom of Death Valley evaporates. Click on image for full size (66K JPG)

Courtesy of Martin Miller, University of Oregon

ExamplesExamples LimestoneLimestone

made when made when calcite calcite mineral mineral precipitates precipitates from sea from sea water .water .

Rock SaltRock Salt——made from made from evaporation evaporation of sea waters.of sea waters.