Exam 1 --- Geoscience

Crust

The thin, outermost layer of the Earth consisting of continental and oceanic crust.

Mantle

The thick layer beneath the crust, composed of silicate rocks rich in iron and magnesium.

Outer core

The liquid layer of the Earth made of molten iron and nickel.

Inner core

The solid sphere at the center of the Earth, composed mainly of iron and nickel.

Planetary accretion, heat collisions, and radioactive decay

Processes that contributed to the Earth acquiring its internal heat.

Lithosphere

The strong outer shell of the Earth consisting of the crust and the uppermost layer of the mantle, which can break but does not readily flow.

Asthenosphere

The weakest layer of the mantle that flows readily and underlies the lithosphere, allowing tectonic plates to slide over it.

Continental drift evidence

Wegner's evidence included the fit of continents like a puzzle, paleoclimate indicators, structural similarities of rocks, and fossil distributions.

Magnetic lineations

Patterns on the ocean floor that indicate past reversals of Earth's magnetic field.

Mid-ocean ridge

An underwater mountain range where new oceanic crust is formed; exemplified by the Mid-Atlantic Ridge.

Subduction zone

A convergent boundary where one tectonic plate sinks beneath another, like the Japan Trench.

Transform plate boundary

A boundary where tectonic plates slide past each other horizontally, such as the San Andreas Fault.

Passive plate margin

The boundary between continental crust and oceanic crust that is not a tectonic plate boundary, as seen on the Eastern U.S. coast.

Supercontinent

A massive landmass formed by the merging of multiple continents, such as Pangaea.

Wilson cycle

The cycle describing how continents break up and then rejoin through formation, expansion, contraction, and closure due to plate movements.

Convection in crystalline solids

Convection cannot occur in crystalline solids because it requires fluid-like behavior; heat is conducted instead.

Driving forces of plate tectonics

The movement of tectonic plates is driven by mantle convection, slab pull, and ridge push.

Earth's magnetic field components

Requirements for Earth's magnetic field include a liquid outer core, rotation of Earth, and convection currents in the molten iron.

Consequences of losing magnetic field

Problems include issues with electrical grids, potential visibility of Auroras everywhere, more charged particles impacting Earth, navigational difficulties for migratory animals, and no mass extinctions.

Largest earthquakes (1960 Chile)

The most significant earthquake in the last 100 years, measuring 9.5 on the Richter scale.

Elastic rebound

The process where crust bends like rubber, storing energy, and then unbends, releasing energy.

Stick-slip behavior

The behavior where faults remain stuck while energy builds and then suddenly slip when enough energy is released.

Asperity

Rough spots along a fault that store stress and release it during earthquakes, resulting in intense shaking.

Thrust fault

Occurs at convergent boundaries where plates collide and compress.

Normal fault

Occurs at divergent boundaries where tectonic plates pull apart and extend.

Strike-slip fault

Occurs at transform boundaries where plates slide past one another horizontally.

Seismic waves

Vibrations that travel through the Earth; include P-waves, S-waves, and surface waves.

Triangulating an earthquake epicenter

Requires three seismograms to locate the epicenter of an earthquake.

Outer core as liquid

Determined by the absence of S waves in the outer core but presence of P waves.

Earthquake magnitude vs. intensity

Magnitude refers to the energy released, while intensity refers to the shaking felt.

Theoretical earthquake maximum

The maximum earthquake magnitude cannot exceed 10; every whole number increase in magnitude results in a 10-fold increase in amplitude.

Loose sediments and earthquakes

Loose sediments amplify seismic waves, leading to increased intensity and potential structural damage.

Mercalli Scale

Measures the intensity of shaking that people feel during an earthquake based on felt reports.

Seismic wave transmission in the US

Older, denser bedrock in the eastern US transmits seismic waves more efficiently than the younger, fractured crust in the western US.

Biggest vs. deadliest earthquakes

Biggest earthquakes arise from the largest stress build-up, while deadliest earthquakes are influenced by population density and building practices.

Challenges in earthquake prediction

Complications arise from the lack of reliable precursors, inability to measure stress in the Earth, and unknown thresholds for initiation of earthquakes.

Forecasting earthquake probabilities

Based on slip deficit rates and the time since the last earthquake.

Problem with earthquake precursors

Currently, there are no consistent precursors; behaviors such as foreshocks are unreliable indicators.

GPS in earthquake forecasting

GPS measures slip deficit rates to forecast the potential size of future earthquakes.

Seismic hazard in the Midwest

Inferred from historical data of significant earthquakes in the New Madrid region.

Minimizing earthquake deaths

Recommendations include staying indoors and taking cover, moving out of buildings in developing countries, and staying away from structures outdoors.

Diagonal beams in buildings

They provide resistance against shearing forces that can cause buildings to collapse during earthquakes.

California building standards

Require a 90% chance of avoiding total building collapse in the event of a major earthquake.

Importance of foundations and liquefaction

Proper foundations prevent building collapse during earthquakes; liquefaction turns wet soil into fluid, compromising stability.

Preventing building sway during earthquakes

Base isolation systems allow buildings to move independently from their foundations, reducing sway.

Earthquake early warning systems

These systems detect seismic waves and communicate warnings before shaking begins, leveraging the slower speed of seismic waves compared to light.