Ch. 3.3+3.4 notes: Sedimentary and Metamorphic Rockslwcearthscience.yolasite.com/resources/Ch 3.3+3.4 (Bakke) notes.pdf · Ch. 3.3+3.4 notes: Sedimentary and Metamorphic Rocks Author:

Ch. 3.3+3.4 notes: Sedimentary and Metamorphic Rocks

Objective

• Understand how sed. And met. Rocks form

• Understand the types of sedimentary processes

• Understand the agents of metamorphism

Sedimentary rocks

• Sedimentary rocks form when solids settle out of a fluid such as water or air

• Sediment comes from the latin

word “sedimentum” which means settling

Where does sediment come from?

Weathering V. Erosion

• Weathering is any process that breaks rock into smaller pieces called sediment

• There are two types of weathering, physical and chemical

Weathering V. Erosion

• Weathered sediments don’t usually remain in place

• Erosion is the process that transports sediments from one place to another

• Water, wind, ice, or gravity

Deposition

• Deposition occurs after the sediments have been transported

• Sediments are placed down or deposited

Compaction

• Compaction is the process that squeezes or compacts sediments together

• This compaction turns the sediments into rocks

Cementation

• Cementation is a process when disolved minerals are deposited in tiny spaces in sediment

• The sediments harden to form a rock

Classifying Sedimentary rocks

• Clastic Sedimentary rocks

– Made from weathered bits of rock material

• Chemical Sedimentary rocks

– Dissolved minerals precipitate out of a water solution (deposit)

Features of Sed. Rocks

• Sometimes sedimentary rocks have features that indicate the type of environments that they formed in

Metamorphic Rocks

• Metamorphic rocks form when pre-existing rocks change due to intense heat and pressure

– The word metamorphic literally means “change in form”

Types of metamorphism • Contact metamorphism

– Hot magma moves into the rock

– The heat from the magma changes the surrounding rock

– Low grade (not much change)

Types of metamorphism

• Regional Metamorphism

– Mountain building

– Large areas of rock are compressed to extreme pressures

– Temperatures can get very hot

– High Grade (lots of change)

Agents of Metamorphism • Heat

– Heat adds energy to the rock which induces chemical reactions to change the minerals in the rock

• Pressure

– The force of pressure can rearrange minerals in the rock

• Reactions in solution

– Hot fluids can dissolve certain minerals and recrystalize new ones

Classifying Metamorphic Rocks

• The texture of metamorphic rocks can either be foliated or non-foliated

Foliated Metamorphic Rocks

• Some met. Rocks change to be more compact or dense creating layers

• Foliated rocks have a layered or banded appearance

Non-Foliated Metamorphic Rocks

• Non-foliated rocks don’t have the distinct layered appearance

• Rather are considered to be massive or lumpy