MIDTERM 1

normal fault

A type of fault where the hanging wall slides downward; caused by tension in the crust DIVERGENT BOUNDARY

types of transform plate boundaries

1. oceanic - between ridge settlements 2. continental

fault

A break in the earth's crust which may or may not generate an earthquake most commonly along plate boundaries and not inside continents

Seismograph; How do we stand still and watch Earth move?

A device that records ground movements caused by seismic waves as they move through Earth; • Heavy weight suspended from a rigid column anchored to ground stays still from its own inertia while ground moves • Weight is suspended from a wire or spring depending on the direction of motion measurement

Ring of Fire

A major belt of volcanoes that rims the Pacific Ocean

Uniformitarianism

A principle that geologic processes that occurred in the past can be explained by current geologic processes; The natural world has been formed by many small incremental and gradual events These events occur constantly; rock strata demonstrate that geological processes add up over long periods of time to cause great change

Catastrophism

A principle that states that geologic change occurs suddenly; the natural world has been shaped by very few events, each of very short duration and great significance; in between these events all is static and unchanging the earth is young (only a few thousand yrs)

Lithosphere

A rigid layer made up of the uppermost part of the mantle and the crust; cold and rigid (tectonic plates) mode of heat transfer: conduction (direct molecular interaction or physical contact) broken into 12 large parts and 12 small parts

Richter scale

A scale that rates an earthquake's magnitude based on the size of its seismic waves; limitations: It saturates for larger earthquakes, failing to accurately represent their true magnitudes. It is most accurate for earthquakes occurring within 600 kilometers (370 miles) of the seismograph station ----> Moment Magnitude Scale (Mw) is preferred for every increase in amplitude by 10 richer magnitude increases by 1

what is the oldest rock in the world?

Acasta Gneiss, in northern Canada (4.02 billion years Controversial -> Nuvvuagittuq greenstone belt in canada

divergent plate boundary

Boundary between tectonic plates in which the two plates move away from each other

convergent plate boundary

Boundary between tectonic plates in which the two plates move twords from each other Convergent boundaries -- where crust is destroyed as one plate dives under another. Transform boundaries -- where crust is neither produced nor destroyed as the plates slide horizontally past each other.

transform plate boundary

Boundary between two plates that are sliding past each other in opposite directions Convergent boundaries -- where crust is destroyed as one plate dives under another. Transform boundaries -- where crust is neither produced nor destroyed as the plates slide horizontally past each other.

Surface Waves (Rayleigh and Love)

Confined to interfaces (interfaces between regions with different physical properties) • Intermediate frequency, period, and wavelength

With existing technology, it is possible to predict earthquakes to withina few days.

False

true/false The peak Mercalli intensity for an earthquake is determined using the maximum amplitude of body waves recorded on a seismogram.

False. The peak Mercalli intensity for an earthquake is not determined using the maximum amplitude of body waves recorded on a seismogram. The Mercalli intensity scale is a subjective scale that assesses the observed effects and damage caused by an earthquake at specific locations. It is based on observations and reports from people who experienced the earthquake rather than instrumental measurements.

true/false The Earth's surface thermal gradient (rate of change of temperature with depth, measured at the surface) has generally increased over time.

False; The Earth's surface thermal gradient, which refers to the rate of change of temperature with depth, measured at the surface, has not consistently increased over time.

Hazard vs. Risk

Hazard = an event that could cause serious harm Risk = the probability that the hazard could happen

Wavelength

Horizontal distance between the crests or throughs

What kind of faulting would you expect at a transform plate boundary? 1. Normal faulting 2. Thrust (or reverse) faulting 3. Strike-slip faulting

In strike-slip faulting, the movement along the fault is predominantly horizontal, with minimal vertical displacement. The two blocks of crust slide past each other horizontally, parallel to the strike (the direction of the fault line).

What is the mid ocean ridge and how is it formed?

Longest mountain chain in the world. Curves along sea floor into all oceans. Forms along a crack in the oceanic crust. Molten material rises up, erupts, and spreads out. A mid-ocean ridge is a long underwater mountain range that runs through the floor of the world's oceans. It is formed by tectonic plate spreading, where two tectonic plates diverge or move away from each other. key characteristics: areas of high tectonic and volcanic activity

Free oscillations (= normal modes)

Lowest frequency, not damaging, frequency and wavelength too low

what does it mean for disasters to be fractal?

Many natural features and processes are fractal - they have similarities across a range of size; look the same regardless of size Picture of a branch of a tree but part of a larger tree

What is mitigation of natural disasters?

Mitigation involves efforts to avoid disasters rather than merely dealing with the resulting damages. Ie. not building dams that impact the flow of large amounts of water

The youngest oceanic crust is found?

Near mid-ocean ridges

On a _______ fault, the hanging wall lock slips down the surface of the fault, relative to the footwall. If the fault displaces the ground surface, a _______ develops.

Normal/ fault scarp

Liquefaction

Occurs when wet soil acts more like a liquid during an earthquake; happens when loosely packed water logged sediments at or near the ground surface loose their strength in response to earthquakes.

oceanic vs continental crust rock composition

Oceanic crust is primarily composed of basaltic rocks; continental crust consists mainly of granitic rocks

How does oceanic crust differ from continental crust in terms of chemical or mineralogical content, density, and thickness? In the context of one or more of these characteristics, explain why a continental plate never subducts.

Oceanic crust is primarily composed of basaltic rocks; continental crust consists mainly of granitic rocks Oceanic crust is denser than continental crust. Oceanic crust is thinner compared to continental crust. When an oceanic plate encounters a continental plate at a convergent plate boundary, subduction often occurs, with the denser oceanic crust being forced beneath the lighter continental crust; the continental crust tends to resist subduction and is typically uplifted or undergoes deformation during the collision with an oceanic plate.

size of earthquakes (offset and surface rupture length)

Offset: distance of movement across fault Surface rupture length: total length of break

body waves; P and Swaves

P and Swaves seismic waves that travel through the Earth's interior high frequency short period and short wavelength; faster than surface waves p - primary; faster than s waves arrive first s - secondary; slower than p waves

sequence of seismic waves

P-waves are first S-waves are second Surface waves are last

why you could not use a radioactive element with a half-life of 5 years to date rocks

The half-life of 5 years is relatively short compared to the geological time scale. Rocks on Earth can be millions or even billions of years old. Using a radioactive element with such a short half-life would limit the dating range to only a few half-lives, providing a narrow time window for accurate dating.

According to the "elastic rebound theory" of earthquake generation:

Rock bends elastically before breaking; the sudden break and/or frictional sliding causes earthquakes

Stress vs. Strain

Stress: stress in posed on a rock; force applied on a rock; intensity of the internal forces within a rock Strain: changes in rocks shape in response to stress

continental drift

The hypothesis that the continents slowly move across Earth's surface.

To locate the epicenter of an earthquake, what information do you need?

The difference in arrival times of the P and S waves, as recorded at three different stations

Mantle vs. Core of Earth

The mantle is the layer of the Earth located between the crust and the core. It is the largest layer of the Earth, accounting for about 84% of its total volume. The mantle is primarily composed of solid rock, with high concentrations of silicate minerals rich in iron and magnesium. The core is the innermost layer of the Earth, located beneath the mantle. It is divided into two parts: the outer core and the inner core. Hugh tempratures; generates earth magnetic field

Asthenosphere

The soft layer of the mantle on which the lithosphere floats. weak because it can flow but hot and solid NOT liquid, more easily deformed mode of heat transfer: conduction and convection (transfer of heat through fluids like gas and liquids)

what type of scale is used to plot the recurrence interval of natural disasters and why?

The type of scale commonly used to plot the recurrence interval of natural disasters is a logarithmic scale. The recurrence interval represents the average time between successive occurrences of a particular natural disaster event, such as earthquakes, floods, or hurricanes. Since the recurrence intervals can vary over a wide range, spanning from short periods to very long periods, a logarithmic scale is used to effectively represent this wide range of values on a single graph.

continental drift: magnetic field direction

When molten rock cools and solidifies, it can preserve the orientation of Earth's magnetic field at that time. This is because certain minerals in the rock, such as magnetite, align themselves with the magnetic field while they are forming. By studying the magnetic properties of rocks, scientists can determine the direction and intensity of the Earth's magnetic field at the time the rocks were formed.

Moment magnitude

a more precise measure of earthquake magnitude than the Richter scale, which is derived from the amount of displacement that occurs along a fault zone and estimates the energy released by an earthquake; logarithmic scale that measures the total energy released by an earthquake. It provides a more accurate and comprehensive estimate of earthquake magnitude compared to the Richter scale, especially for larger and more powerful earthquakes. The Mw scale takes into account the seismic moment, which is a measure of the area of the fault that slipped, the average amount of slip along the fault, and the rigidity of the rocks involved.

thrust fault

a reverse fault in which the hanging wall slides over to the foot wall. CONVERGENT BOUNDRY

fault scrap

a small step on the ground surface where one side of a fault has moved vertically with respect to the other; steep slope or cliff along fault line due to tectonic activity

strike-slip fault

a type of fault where rocks on either side move past each other sideways with little up or down motion TRANSFORM BOUNDRY

reverse fault

a type of fault where the hanging wall slides upward; caused by compression in the crust CONVERGENT BOUNDRY

What are metamorphic rocks?

any rock that forms from another rock as a result of changes in heat or pressure (marble)

Layers of the Earth (rheological subdivisions)

asthenosphere and lithosphere

silica tetrahedron a) An ultra-sensitive structure in a seismometer. b) A component of many rock-forming minerals. c) The area in California that is most at risk for earthquakes. d) The region of the mantle that is the source for most magmas erupted on at divergent plate boundaries. e) An ancient Egyptian pyramid f) None of the above

b) A component of many rock-forming minerals. a grouping of one silica ion and four oxygen ions that forms the basic building block of a silicate

The commonly accepted hypothesis for the formation of the planets, including Earth, is a) a supernova explosion b) the gravitational accretion of a cloud of gas, ice, and solid material c) the collision of two meteorites d) an eruption from the Sun e) nuclear fission

b) the gravitational accretion of a cloud of gas, ice, and solid material

Layers of the Earth (compositional subdivisions)

crust, mantle, core core - iron and nickel mantle (below lithospheric crust) - silicate, iron, calcium, magnesium crust (lithospheric crust)- mainly peridotite

strike-slip vs dip-slip faults

dip-slip: reverse/normal up or down movement strike-slip: left or right lateral and parallel horizontal movement

stress vs strain process of rocks

elastic deformation (reversible) ---> plastic deformation (not reversible) ---> brittle failure, fault slips (earthquake) stress and strain increase from --->

Subduction zones are commonly associated with ________________. a) chains of volcanoes b) a downwards-slanting plane of earthquake hypocenters c) a deep ocean trench d) answers a and b e) answers b and c f) answers a, b, and c g) none of the above

f) answers a, b, and c

true/fasle If all of geologic time were represented by a 24 hour day (midnight to midnight), humans would enter the scene around 6 pm.

false

true/false: The Earth's core is composed of ultramafic rock.

false The core is primarily composed of iron and nickel, with trace amounts of lighter elements such as sulfur and oxygen; ,pre metallic than being composed of a rock

true/false The terms lithosphere and crust are synonymous (mean the same thing).

false The lithosphere refers to the rigid outer layer of the Earth, which consists of the crust and the uppermost part of the mantle. It is a tectonic plate that is broken into several pieces, and it is involved in the movement and interaction of these plates. On the other hand, the crust refers specifically to the outermost layer of the Earth's lithosphere.It is the thinnest layer and can be divided into two main types: oceanic crust, which forms the ocean basins, and continental crust, which forms the continents and larger land masses.

true/false A lithospheric plate can contain either oceanic crust or continental crust, but not both.

false; A lithospheric plate can indeed contain both oceanic crust and continental crust. Lithospheric plates are large segments of the Earth's outer shell, consisting of the crust and the uppermost part of the mantle. These plates can have various configurations and can include a combination of oceanic and continental crust.

true/false The guiding principle behind the determination of the frequency of natural disasters is uniformitarianism, i.e., that the processes that have happened in the past will continue to happen in the future, and at similar rates.

false; When it comes to the frequency of natural disasters, including earthquakes, volcanic eruptions, hurricanes, and floods, the principle of uniformitarianism is not directly applicable. Natural disasters are influenced by a combination of geological, climatic, and other factors that can vary over time.

true/false Convection refers to the transfer of heat by direct contact between two substances with different temperatures.

false; that is conduction convection is the transfer that involves liquid or gas

true/false Rayleigh and Love waves are both types of body waves.

false; they are types of surface waves

Why do we determine the age of Earth from extraterrestrial rocks (meteorites) and not from the oldest rocks formed on Earth?

finding intact, undisturbed rocks that formed during Earth's early history is challenging; The surface of the Earth has undergone significant changes over billions of years, including the destruction, erosion, and burial of ancient rocks. As a result, the oldest rocks on Earth that have been preserved are generally found in remote, inaccessible areas or are deeply buried beneath layers of younger rocks.; Dating the oldest rocks on Earth poses technical challenges. The most common dating methods, such as radiometric dating, rely on the decay of radioactive isotopes to determine the age of rocks. However, the Earth's oldest rocks have undergone extensive alteration and metamorphism, which can reset the radiometric clock or make dating unreliable.

What are sedimentary rocks?

formed from layers of sand, silt, dead plants and animal skeletons (chalk and sandstone); accumulation and compaction of minerals or organic materials, such as sand or mud.

continental drift: continental glaciation

glaciers on the bottom of the continents illustrating that ice sheets existed (they where attached to the pole Antarctica)

continental drift: polar wander curve

if we assume poles are fixed, if the continent movies in some orientation the magnetic field moves with the continent, if we trace back in time we can see the continents where near one another and then drifted apart

Rock Categories

igneous, sedimentary, metamorphic

Subduction zone

in tectonic plates, the site at which an oceanic plate is sliding under a continental plate; denser plate slides into the asthenosphere

Collision Zones

low density continents crumple into each other

Types of convergent plate boundaries

oceanic-oceanic, oceanic-continental, continental-continental

plastic deformation

permanent change in shape by bending and folding of rocks; high stress conditions in earth; unlike elastic deformation, which is reversible and temporary, plastic deformation involves the permanent rearrangement of atoms or crystals within the rock.

radioactive decay of rocks

rate at which radioactive atoms decay (number per unit time) is proportional to the number of atoms present

continental drift: distribution of volcanoes

ring of fire

Rock vs. Mineral

rock: an assemblage of minerals bound together, usually 2 to 5 different materials mineral: solid, naturally-occurring substance with ordered arrangement of atoms, and a specific composition or range of composition

What are ingenious rocks?

rocks formed when melted magma or lava cools (granite and pumice)

Mercalli Intensity Scale

scale of earthquake intensity based on what people feel and the extent of damage caused by the earthquake

elastic rebound theory

scientific explanation for why earthquakes happen; The theory that continuing stress along a fault results in a buildup of elastic energy in the rocks, which is abruptly released when an earthquake occurs.

continental drift: jigsaw puzzle

shape of continents fit together like a puzzle

half-life

time for half of a population of radioactive parent atoms to decay to daughter atoms To find the amount of an element to decay after a certain number of half lives x = (½^x)

continental drift: fossils

trends of fossils between continents

The concept that actions of people can somehow cause or "induce"seismicity is only a myth.

true

true/false Free oscillations (normal modes) have the shortest periods of all types of seismic waves.

true

true/false Half-life is defined as half the time it takes all radioactive atoms of a particular isotope to decay to their daughter isotope.

true

true/false The first type of wave to arrive at a seismic station after an earthquake is a P wave.

true

true/false The point on the Earth's surface above where a fault first ruptures in an earthquake is known as the epicenter.

true The point on the Earth's surface directly above the location where a fault first ruptures in an earthquake is known as the epicenter. It is the point of the Earth's surface closest to the initial seismic energy release and is typically the location where the earthquake's effects are most strongly felt.

continental drift: age of seamount chains

underwater mountains formed by volcanic activity; As the Earth's tectonic plates move, seamount chains are carried along with them. By studying the ages of different seamounts in a chain, scientists can estimate the rate and direction of plate motion.

Why does volcanism occur near convergent plate boundaries?

volcanism is caused by convergent plate boundaries; when tectonic plates collide, it generates magma and high pressure expelled through volcanoes

amplitude of a wave

½ vertical distance between crest and through

How much and how long the ground shakes during an earthquake depends on

• How much the fault has moved • Where fault has moved • Local conditions amplify shaking and increase damage

Why are travel time curves of seismic waves not straight lines?

•P and S wave velocities increase with depth in the earth. Waves that penetrate deeper have faster average velocities

fault slips; foreshocks, aftershocks

▪ Foreshocks: smaller slips as fault begins to fail ▪ Aftershocks: slips as fault continues to adjust after main shock