Hazards and Earthquakes Flashcards

Flashcards on Hazards and Earthquakes

Hazard

A threat (natural or human) that can cause loss of life, injury, property damage, socioeconomic disruption, or environmental degradation

Hazard Event

The occurrence of a hazard, the effects of which change demographic, economic, and/or environmental conditions

Disaster

A major hazard event that causes widespread disruption to a community/region, where the affected community is unable to deal with it adequately without outside help

Geophysical Hazards

Natural hazards occurring due to the earth’s tectonic processes and internal structure

Crust

The outermost and thinnest layer of the Earth, composed of oxygen, silica, and aluminum

Silica and Aluminium

Continental crust is made of?

Silica and Magnesium

Oceanic crust is made of?

Mantle

The middle layer between the crust and the core, composed of magnesium and iron silicates

Core

The innermost layer of Earth, composed of iron and nickel

Lithosphere

The crust and uppermost mantle, broken up into tectonic plates

Asthenosphere

The upper mantle not in the lithosphere, a semi-liquid or molten layer

Continental Drift Theory

Alfred Wegener's theory that the earth was made up of a single super continent surrounded by one ocean.

Pangea

The name of the super-continent in the continental drift theory

Panthalassa

The name of the ocean that surrounded Pangea

Oceanic Ridges

Great mountain range on the ocean floor that provided proof of sea floor spreading

Closest to oceanic ridge

Younger rocks are located where, relative to a ridge?

Further away from ridge

Older rocks are located where, relative to a ridge

Benioff Zones

Concentration of earthquake activities that coincide with oceanic trenches and ridges

Theory of Plate Tectonics

The theory that the Earth’s crust/lithosphere is made up of separate tectonic plates, which move above a molten mantle.

Primordial Heat

Heat lost by earth as it continues to cool from original formation

Radiogenic Heat

Radioactive decay of materials in the mantle and crust

Plume (Hotspot)

A small area of unusually high heat flow that can cause movement; responsible for the original rifting of crust

Divergent (Constructive) Plate Boundary

A plate boundary where two plates move away from each other, forming new crust

Convergent (Destructive) Plate Boundary

A plate boundary where two plates move towards each other, resulting in the destruction of the lithosphere

Transform Plate Boundary

A plate boundary where plates move past each other in a parallel manner, neither creating nor destroying lithosphere

Mid-Oceanic Ridge

A long chain of submarine mountain ranges formed at divergent oceanic-oceanic plate boundaries

Graben (Rift Valley)

Major elongated depression formed when continental crust is ripped apart at divergent continental-continental plate boundaries

Horsts

Block mountains formed when continental crust is ripped apart at divergent continental-continental plate boundaries

Oceanic and Continental

A deep oceanic trench and volcanic mountain chains are formed when the denser plate subducts beneath plate

Continental-Continental Plate Boundary

Fold mountains that occur due to the collision of lithospheres, causing massive crustal deformation

Transform Fault

The plane along which the motion occurs in a transform plate boundary

Pacific Ring of Fire

Located around the Pacific Ocean, marked by high volcanic and seismic activity

Eurasian-Indonesian (Alpide) Belt

A major belt of volcanic and seismic activity stretching from North Africa through the Alps and Himalayas to the Pacific Ring of Fire

Volcanoes

Cone-shaped structures that form when magma reaches the earth’s surface, causing eruptions of lava and ash

Magma Chamber

The collection of magma inside the earth, below the volcano

Main Vent

The main outlet for magma to escape from a volcano

Secondary Vent

A smaller outlet through which magma escapes from a volcano

Crater

Created after an eruption that blows the top off a volcano

Shield Volcanoes

Low, gently sloping volcanoes with a shallow crater and large circumference, formed from lava flows with low viscosity

Composite Volcanoes

Volcanoes with a high, steep profile due to rhyolitic/andesitic lava containing high levels of silica and high viscosity

Cinder Volcanoes

Simple volcanoes that form when solid material and lava blobs are ejected from a volcanic vent

Hawaiian Eruption

The calmest type of lava eruption, characterized by the effusive eruption of very fluid basalt lavas with low gas and silica content

Pahoehoe Lava

A relatively smooth lava flow with a ropey appearance, moving as a sheet due to its less viscous nature

A’a Lava

A denser and more viscous lava that tends to move more slowly, with outside layers cooling into a rubble-like mass

Strombolian

Pyroclastic, named after volcano stromboli

Vulcanian

Pyroclastic, named after volcano vulcano

Pelean/Nuee Ardente

Pyroclastic, named after volcano Mount Pelee

Vessuvian/Plinian

Pyroclastic, named after Mt. Vesuvius

Volcanic Explosive Index (VEI)

Measured on a scale of 0-8, indicating the amount of material ejected and damage caused by a volcanic eruption

Pyroclastic Flows

High-density mix of hot lava blocks, pumice, ash, and volcanic gas that moves at very high speeds

Lahars

Hot or cold mixture of water and rock fragments that flows down the slopes of a volcano

Volcanic Landslides

Very large masses of wet/dry rock and soil that fall/slide/flow very rapidly under the force of gravity

Earthquake

Rumbling/trembling of the ground produced by breaking rocks in response to geologic forces within the earth

Focus

The point of origin of an earthquake within the crust, where stress is released

Epicenter

The point on the earth’s surface directly above the focus of an earthquake

Body Waves

Transmitted upwards towards the surface of the earth from the focus of the earthquake

Primary Waves

Seismic waves that are almost 2x faster than other waves, longitudinal, and travel through any type of material

Secondary Waves

Seismic waves that are also known as shear waves, shaking the ground perpendicular to the direction in which they propagate.

Rayleigh Waves

Causes the ground to move up and down in ripples, producing shaking movement felt during earthquakes

Love Waves

Causes the ground to move sideways, producing a rolling feeling during earthquakes

Richter Scale

What scale measures the magnitude of an earthquake via total amount of energy released by seismic waves from its source?

Mercalli Scale

What scale measures the intensity of the earthquake is a descriptive measure of the degree of shaking in terms of the damage caused and other effects?

Different Subduction

Earthquakes occur at all types of boundaries, but characteristics differ depending on?

Instability and Earthquakes

Removal of material from earth means what, and can trigger what?

Earthquakes and Aftershocks

These 2 hazards relate to most building and structural damage, injuries, damage to gas pipes and communication lines, transport infrastructure and deaths

Landslides

Masses of rock, earth, or debris that move down a slope

Liquefaction

Earthquake effect where loose sand and silt saturated with groundwater results in the soil behaving like a liquid, causing structures to lose support

Fault

A break in the rocks that make up the earth’s crust, along which rocks on either side have moved past each other

Transverse Faults

Occur when a block of rock fractures, and two blocks of rock slide past each other in opposite directions

Mass Movement (Landslide)

The movement of regolith and masses of rock downslope under the pull of gravity

Shear Stress

Force which causes movement of body parallel to slope

Shear Strength

Internal resistance of body to movement

Angle of Repose

Steepest angle at which pile of unconsolidated grains remains stable and stationary

Joints and Fractures

Breaks of natural origin in the continuity of either a layer or body of rock

Slope failure and Sediment Flows

The two main groups mass movement processes are classified into

Slumps

Types of slides where downward rotation of rock/regolith occurs along curved surface

Rock Falls

Occur when a piece of rock on a steep slope becomes dislodged and falls down the slope

Sediment Flows

Mixture of rock, regolith and water, occurring when sufficient force is applied to rocks and regolith such that they begin to flow downslope

Slurry Flows

Sediment flows containing 20-40% water

Granular Flows

Sediment flows containing 0-20% water

Solifluction

Very slow downslope movement of saturated soil and regolith

Debris Flows

Downslope movement of unconsolidated regolith, often resulting from heavy rains

Creep

Very slow, continuous movement of regolith downslope

Mudflows

Highly fluid, high velocity mixture of sediment and water with consistency of wet concrete

Grain Flows

Movement of relatively dry granular sediment

Debris Avalanches

Very high velocity flows of large volume mixtures of rock and regolith resulting from complete collapse of mountainous slope