ERTH20 Exam 2

Atom

The smallest unit of matter that has properties of a chemical element.

Ion

An electrically charged atom.

Element

A substance consisting of one type of atom.

Mineral

A naturally occurring inorganic solid with an ordered internal structure of atoms and a definite chemical composition

Rock

An aggregate of minerals.

Streak

The color of a mineral in its powdered form.

Cleavage

When minerals break along planes of weak chemical bonding.

Mineral with yellow streak

Sulfur.

Mineral with cubic shape (habit)

Halite.

Ionic substitution

When one ion replaces another in a mineral’s crystal structure

Most abundant elements in Earth’s crust

Silicon and oxygen.

Silicon-oxygen tetrahedron

The building block of silicate minerals that bonds with other tetrahedrons.

Light-colored silicate minerals

Quartz

Dark-colored silicate minerals

Olivine

Oxides

Weathered metallic minerals.

Example of oxide mineral

Hematite.

Example of carbonate mineral

Calcite.

Evaporite minerals

Carbonates

Crystal size

Indicates magma cooling history (large = slow cooling

Igneous rock textures

Phaneritic

Bowen’s Reaction Series

Describes the sequence in which minerals crystallize as magma cools.

Felsic composition minerals

Potassium feldspar

Volcano eruptions produce

Lava

Viscosity

A measure of a material’s resistance to flow.

Silica content and viscosity

High silica = high viscosity; low silica = more fluid.

Magma with most silica

Rhyolitic magma.

Magma with least silica

Basaltic magma.

Rocks erupting from stratovolcanoes

Intermediate to felsic igneous rocks.

Metamorphic changes

Recrystallization and new mineral growth.

Agents of metamorphism

Heat

Settings of metamorphism

Regional (mountain building) and contact (near magma).

Foliation

Alignment of platy minerals caused by directed pressure.

All rocks foliated?

No.

Highest-grade foliated rock

Gneiss.

Lowest-grade foliated rock

Slate.

Role of chemically active fluids

Promote new mineral growth by enhancing ion migration.

Fluids creating ore deposits

React with parent rocks and change their composition.

Metamorphic index minerals

Form at specific temperatures and pressures; indicate metamorphic grade.

Physical vs chemical weathering

Physical breaks rock into pieces; chemical alters composition.

Types of mechanical weathering

Frost wedging

Types of chemical weathering

Oxidation

Factors affecting chemical weathering

Rainfall and temperature.

Most resistant minerals

Quartz

Soil components

Mineral matter

Factors controlling soil formation

Time and climate.

Origins of sedimentary rocks

Weathered rock

Formation of detrital rocks

Weathering and erosion.

Sediment transport

Rivers and wind.

Depositional environment

Place where sediment is deposited.

Lithification

Compaction

Wentworth Scale

Relates grain size to transport energy.

Sediment deposit prediction

Smaller grains travel farther offshore.

Grain shape

Rounder grains = transported farther from source.

Sorting

Uniformity of grain size.

Porosity

Spaces between sediment grains.

Chemical sediment

Mineral crystals or chemical residue.

Detrital sediment

Fragments from weathered rock.

Biochemical sediment

Material from organisms (shells

Classification of detrital rocks

Based on grain size

Common trait of biochemical rocks

React with CaCO₃.

Rocks reacting with HCl

Contain CaCO₃.

Formation of inorganic sedimentary rocks

Precipitate from water or form chemically after burial.

Sedimentary structures

Physical clues showing depositional processes and environment.

Forces on slopes

Normal force and shear force.

Factor influencing slope movement

Angle of repose.

Common triggers

Water saturation

Water effect on slope stability

Increases weight and reduces strength.

Vegetation effect on slope stability

Roots reinforce soil and absorb water.

Creep

Slow downslope movement; tilted fences indicate it.

Solifluction

Slow soil flow in permafrost regions.

Mass wasting classification

Based on material

Mitigation strategy

Grading.

Work of a river

Energy of flowing water shaping landscapes.

Steepest river gradient

Near headwaters.

Lowest river gradient

In meandering sections.

Gentle vs steep stream gradient

Gentle = wide meanders; steep = V-shaped valleys.

Stream gradient formula

Gradient = change in elevation ÷ horizontal distance.

Base level

Lowest point a river can erode.

Factors changing base level

Human activity or natural events.

Gradient change with base level

Adjusts along the river’s length.

Sediment load types

Dissolved load

Point bar

Deposition on the inside of a meander.

Erosion location

Outer bends of meanders.

Meandering river

Low-gradient river with looping bends.

Braided stream

Network of channels with high sediment load.

Floodplain during flood

Widens due to meander expansion.

Meanders

Curves formed by erosion and deposition.

Oxbow lake

U-shaped lake from a cutoff meander.

Natural levees

Raised riverbanks formed by sediment deposition.

Flash flood conditions

Intense rainfall.

Regional flood conditions

Long storms or snowmelt.

Land development and flooding

Increases runoff and flood magnitude.

Flood control structures

Dams

Why is the mineral quartz the most common detrital sediment?

It’s hardness and ability to resist

A round particle shape indicates what?

The further the sediment has been moved