Week 4: Sedimentary Rocks classes + Weathering

What are the 4 classes of sedimentary rocks

Clastic

Biochemical

Organic

Chemical

What are the 4 steps required to form sedimentary rocks?

Weathering

Erosion and Transport

Deposition

Lithification

What are the 2 types of weathering?

Physical

Chemical

What are 3 physical weathering processes?

Jointing

Frost Wedging

Root Wedging

What is jointing?

Fractures in a rock

How does jointing occur?

Cooling of magma or lava

Plate Tectonic stresses

Changes in pressure (removal of overlying material)

Layering (bedding) of sediments

What is sheeting?

When large masses of rocks are exposed by uplift and erosion

Fractures parallel to the surface are produced

What happens in frost wedging?

The breaking apart of rocks by freeze-thaw cycles of water in cracks

What happens in root wedging?

Plant roots fracture a rock

What are 3 chemical weathering processes?

Dissolution

Oxidation

Hydrolysis

What happens in Dissolution?

Certain minerals are soluble in water or weak acid

Most important for evaporites (salt deposits) and carbonates (limestones)

What happens in Oxidation?

Rust forms and coats rocks

Involves many mafic minerals

What happens in hydrolysis?

Water reacts chemically with minerals and breaks them down to form other minerals and dissolved ions

Primary mechanism for sillicate weathering

What is the most chemically resistant mineral?

Quartz

What are some weathering products?

Physical:

Particles (clast)

Rock fragments

Mineral fragments

What are some chemical products?

Clay minerals produced by silicate weathering