geological hazards

Minerals

naturally occurring, inorganic solids with a defined chemical composition and regular internal crystal structure

Rocks

naturally-formed, consolidated material composed of grains of one or more minerals

Rock cycle

the process where rocks are continuously formed, broken down, and reformed through geological forces

Sedimentary rock ex

sandstone, mudstone

Igneous rock ex

basalt, granite

Metamorphic rock ex

marble, quartzite

Weathering

physical and chemical breakdown of rocks and minerals

Igneous

forms from cooling magma or lava; when melting and crystallization occurs

Sedimentary

forms by consolidation of deposited particles or minerals precipitated from solution; weathering, sedimentation and lithification contribute

Metamorphic

forms from the recrystallization of preexisting rocks (due to heat, pressure, and or chemical agents)

Sedimentation

the process of eroding rock pieces and transporting them by wind, water, or gravity to a new location (deposition)

Chemical weathering

involves the replacement or alteration of chemical composition

Earthquakes

sudden release of energy stored in rocks that occur along faults

Faults

planes of weakness between two rock masses; a fracture in the Earth

States with highest earthquake risks

washington, oregon, alaska

Human activity and earthquakes

deep-water disposal wells and large reservoirs behind dams are examples of human activity that can cause earthquakes

Possible causes of a tsunami

earthquakes and underwater landslides

Crystalline structure

orderly arrangement of atoms in repeating pattern; influences external form

To determine rock history

consider color, grain size, shape, type, and relationships

Most abundant elements in earth’s crust

oxygen, silicon, aluminum, iron, hydrogen, sodium, manganese, potassium, calcium

Major classes of rock-forming minerals

carbonates, silicates, oxides, halides, native minerals, sulfides, sulfates

Geological time determination

relative dating, correlation, absolute dating

Relative dating

used to understand what happened in which order determined by physical position or order

Superposition

younger rocks deposited on top of older

Cross-cutting and inclusions

rocks cut by a feature must be older than the feature, rocks with pieces of other rocks must be younger

Correlation

connects pieces of geological record together to construct a complete history

Absolute dating

determining age of event or rock using laboratory methods

K-P Extinction

mass extinction (dinos and others); rise of mammals; end of mesozoic era

The great dying

major mass extinction (mostly in ocean); end of paleozoic era

Cambrian explosion

widespread appearance of hard-shelled organisms; precambrian era

Anthropocene

new epoch of geologic time; established by Paul Crutzen in 2002

Common causes of earthquakes

tension (normal faults), compression (reverse faults), horizontal shear (strike-slip faults)

Magnitude

measures amount of energy released

Process of earthquake

stress increases and rocks are strained, stress exceeds rock strength and fault slips (earthquake occurs), stress drops and elastic strain recovers

Stick-slip behavior

the fault sticks then slips during cycle of earthquake

Benefits of volcanoes

fertile soils derived from weathering of volcanic material

Dangers of volcanic activity

nuee ardentes, mudslides, global cooling

Climate cooling and volcanoes

sulfur dioxide compounds are emitted by volcanoes

Floodplains

level expanses near waterways periodically inundated with water

Volcanoes positively shaped earth by

providing raw materials good for farming, producing much of earth’s crust and gaseous emissions contributing to development of early oceans and atmosphere

Human contribution to flooding

cause warming of global climate leading to more extreme water; hardening surfaces (speeds runoff and reduces water infiltration); destroy natural wetlands

Mass wasting

downslope movement of earth materials

Human contribution to mass wasting

logging, house construction, road construction

Soil creep vs landslides

they take different amounts of time to occur

Gullying

development of deep trenches on relatively flat ground

Natural sandy beaches

single storms can create and remove inlets and islands; beach is in constant motion as waves redistribute sediments

Barrier island

long, narrow island that lies between mainland and open sea

Important factors causing mass-wasting

rain, ground vegetation, building on steep slopes

Soil creep

occurs at a measurable rate but doesn’t produce visible signs on a daily basis

Jetties and groins cause downstream problems

they rob locations downstream of sediment

Result of global warming

increase in beach erosion as sea level rises

Magnitude and intensity

an earthquake with a single magnitude can yield variable intensities; different ground surface types can cause variation

Liquefaction

before earthquake- water-saturated sediments, friction between grains (hold sediment together); after earthquake- water surrounds grains, sediments flow like a fluid

Tsunamis

result of faults on seafloor, waves radiate away from fault

Types of volcanoes

scoria cone, shield, composite, volcanic dome

Each increase in magnitude

10x more shaking BUT 32x more energy

Types of eruptions

quiet- lava flow and lava fountain; explosive- dome and eruption column

More viscous eruptions

difficult to flow and traps gas; explosive

Less viscous eruptions

flows easier and gas can escape

Damage from ground motion

landslide, rupture, structural damage,

Shield volcanoes

small summit craters, fluid magma from fissures and scoria cones; fissures fed by dikes

Dikes

cracks connecting magma chamber to surface

Composite volcano

pyroclastic flows, landslides and mudflows, lava flows and domes, eruption column; classic volcano

Ring of fire

highest concentration of composite volcanoes (subduction zones)

Mass movement

downslope movement of surficial rock/soil material under force of gravity

Factors controlling slope stability

angle of repose for material, amount of water, fractures, bedding

Triggers for slope failure

precipitation, volcanic eruptions, sudden shock (earthquake), undercutting slope, overloading slope, changes in land use

Scoria cone

made up of solidified lava

Shield volcanoes

biggest volcanoes (tall and wide)

Common falls, slides, flows

rock/debris fall, rotational slide (slump), debris flow, debris slide, earth flow, rock/debris avalanche

Chemical composition

directly controls the viscosity of magma in a volcano

Flooding

most widespread natural disaster worldwide; most occurs start of spring (snow melt)

Hydrographs

display rate of flow of water past a given point on a river vs time

Recurrence interval

average time between floods of given size; rank annual peak discharges

Flood probability

likelihood of exceeding a particular discharge in a given year; still random

Flash floods

water rises rapidly, due to intense rain and rapid runoff

Coastal floods

result from tides, storms, tropical cyclones, tsunamis, etc

Flooding and pollution

2.5k sites with toxic chemicals in flood-prone areas; chemicals released

Flooding and the mississippi

artificial levees and flood walls as flooding solutions BUT it only transfers the flooding problem further downstream