Envionmental Geology Exam #1

Explain why some volcanic eruptions are explosive and others are quiescent (factors determining the explosivity of volcanic eruptions).

- The two primary factors that determine how magma erupts are its (1) viscosity and (2) gas content- Higher viscosity= more explosive, prevent gasses from escaping, the build-up eventually will lead to an explosive reaction- Lower viscosity= gasses escape more easily - more fluid eruption

List and explain the evidence Wegener presented to support his continental drift hypothesis

1. Continental jigsaw puzzle 2. fossils match across the seas (Glossopertis Fern, Mesosaurus) 3. Rock types and geologic features 4. Ancient Climates.

How old is the Earth?

4.5 billion years old

Distinguish between the hypocenter (focus) and the epicenter of an earthquake. Be able to label them on a diagram.

A fault is a large fracture along which there is movement. When movement occurs, the zone within Earth where rock displacement occurs is termed the hypocenter (focus). The point on Earth's surface directly above the focus of an earthquake is called the epicenter.

What is the difference between a pyroclastic flow and a lahar? Which moves faster?

A pyroclastic flow is an avalanche-like cloud that is a mixture of air, hot ash, and pumice lapilli. A lahar is a very wet, ash-rich debris flow that moves in a relatively fast-moving slurry

What is the view that most geologists held prior to the 1960s regarding the geographic positions of the ocean basins and continents?

Geologists held the view that the ocean basins and continents had fixed geographic positions and were of great antiquity.

Where do tropical cyclones form, and what regions of the world are threatened by these storms?

Hurricanes occur in the Atlantic Ocean and the eastern north Pacific Ocean. Typhoons occur in the western Pacific Ocean. Tropical cyclones occur in the south Pacific Ocean and Indian Ocean.

What happens as hurricanes approach land and why?

Hurricanes usually weaken when they hit land, because they are no longer being fed by the energy from the warm ocean waters. However, they often move far inland, dumping many inches of rain and causing lots of wind damage before they die out completely.

List and describe Earth's four major spheres. Define system and explain why Earth is considered to be a system.

Hydrosphere (Water system), Atmosphere (Air system), Biosphere (Life system), Geosphere (Solid Earth system)

Do all submarine earthquakes produce tsunamis?

Is no because an undersea earthquake creates a tsunami only if it is of sufficient force and there is a violent enough movement of the seafloor to displace a massive amount of water.

Be familiar with the major geologic hazards associated with volcanoes.

Lahars Lava volcanic gases landslides

What are the different types of faults and their recognition criteria?

Normal Fault - an inclined fault in which the hanging wall appears to have slipped downward relative to the footwall Reverse Fault - a type of fault where the hanging wall slides upward; caused by compression in the crust Strike Slip Fault - a type of fault where rocks on either side move past each other sideways with little up or down motion

Compare and contrast the three types of convergent plate boundaries and name a location where each type can be found.

Oceanic to Continental When these two different plates collide or converge, they often produce a young volcano after a long period of time. A subduction zone will be produced, because oceanic crust is denser compared to continental crust. Oceanic to Oceanic Oceanic to oceanic collision can manufacture a sort of volcanic island arcs or underwater volcanoes, that will soon emerge as an island with volcanic peak. Continental to Continental Continental to continental on the other hand, produces mountains and mountain ranges.

What causes most earthquakes on the Earth?

Over tens to hundreds of years, stress builds up from plate movement Eventually, stress along the fault overcomes the frictional resistance, and slip initiates as the rocks break

Summarize the characteristics of shield volcanoes and provide one example of this type of volcano. How do shield volcanoes form?

Shield volcanoes are produced slowly from low-viscosity basaltic lava, lack significant amounts of pyroclastic material, and mostly form on the ocean floor as seamounts. Mauna Loa

Why do slopes develop on the Earth? What factors can control the steepness of a slope?

Slopes can happen do to erosion and what factors are heavy rain fall and landslides.

Which type of volcanoes is the most dangerous, and why?

Stratovolcanoes are considered the most violent they are very explosive, producing toxic gas and flying volcanic fragments

Summarize the characteristics of stratovolcanoes and provide one example of this type of volcano. How do stratovolcanoes form?

Stratovolcanoes have relatively steep sides and are more cone-shaped than shield volcanoes. They are formed from viscous, sticky lava that does not flow easily. The lava therefore builds up around the vent forming a volcano with steep sides

Compare and contrast the types of seismic waves and describe the principle of the seismograph

Surface waves - travel through rock layers, just below Earth's surface Body waves - travel through Earth's interior The inertia of the suspended weight tends to keep it motionless while the recording drum, which is anchored to the bedrock, vibrates in response to seismic waves. The stationary weight provides a reference point from which to measure the amount of displacement occurring as a seismic wave passes through the ground

List the major differences between Earth's lithosphere and asthenosphere and explain the importance of each in the plate tectonics theory.

The lithosphere, consisting of the uppermost mantle and all of the crust, is a colder, stronger, and more rigid outer layer of Earth that sits atop the asthenosphere, which is warmer and weaker. The lithospheric material bends or breaks when stressed, while the asthenospheric material, due to the higher temperature and pressure, flows in response to convective heat from Earth's interior.

What is the difference between the theories of continental drift and plate tectonics

The main difference between plate tectonics and continental drift is that plate tectonics describes the features and movement of Earth's surface in the present and in the past whereas continental drift describes the drifting of Earth's continents on the ocean bed.

What is the angle of repose?

The steepest angle at which a material remains at rest

What factors control the viscosity of a melt, and how does viscosity affect the behavior of magma or lava?

The three factors that influence the viscosity of a lava are temperature, the dissolved gases it contains, and its chemical composition. The viscosity of lava has a direct impact on the type of volcano that forms. For example, lava with low viscosity spread out over a large distance and form shield volcanoes. Lava that is very viscous is associated with explosive volcanic eruptions.

What pieces of evidence were used to support the plate tectonics theory

There is a great deal of scientific evidence in support of plate tectonics. Coastlines on opposite continents appear to fit together like puzzle pieces, indicating that they were once joined. Rock and fossils found in South America match those found in Africa, although there is an ocean in between. This also indicates that the two continents were once joined. Other evidence of plate tectonics include Seafloor spreading, which involves the creation of new crust at divergent plate boundaries.

Can hurricanes cross the equator and why?

They never cross the equator, nor do they occur near it. Hurricanes and cyclones are born in waters at least eight degrees north or south of the equator. The rotation of the earth sends them off on a track that arcs away from the equator

What is a hurricane?

Tropical disturbance: a cluster of thunderstorms that grows in the tropics and lasts for more than a day • Tropical depression: the disturbance circulating around a low-pressure center and has maximum sustained winds with speeds between 37 and 61 km/h (23-38 mph) • Tropical storm: when winds increase to 63-118 km/h (37-73 mph) • Hurricane: when a tropical storm intensifies to the point that it has sustained winds of over 119 km/h (74 mph)

Why the height of tsunami waves rapidly increases when they arrive at the shore

Tsunamis have very long wavelengths in the deep ocean and involve large volumes of water in each wavelength. This is why they can shoal as high as they do as the water gets shallower - the wavelength can decrease by a large proportion, so the amplitude can increase by a lot

Describe the relative motion along a transform fault boundary and locate several examples of transform faults on a plate boundary map.

Two plates slide horizontally past one another without producing or destroying lithosphere

What terms are used to describe tropical cyclones in different parts of the world?

Typhoon cyclones Hurricane

What is "uniformitarianism"? How does "uniformitarianism" contrasts with "catastrophism"?

Uniformitarianism suggests that the geological features of Earth were created in slow incremental changes such as erosion. In contrast, catastrophism states that the Earth has largely been sculpted by sudden, short-lived, violent events.

What are the key factors that control and trigger mass movement processes?

Vegitaion Slope heavy water fall

Explain how the global distribution of volcanic activity (e.g., types of volcanoes) is related to plate tectonics.

Volcanoes occur at both convergent and divergent plate boundaries, as well as in intraplate settings. The effects of volcanic eruptions and climate is ash circulates high in the atmosphere where they block sunlight and cause the weather to be cooler. Humans and volcanoes have existed for the longest for better or worse.

What is a tsunami?

a long high sea wave caused by an earthquake, submarine landslide, or other disturbance.

What are intraplate earthquakes?

earthquakes that occur away from plate boundaries

What four conditions are necessary for hurricane formation?

low air pressure. warm temperatures. moist ocean air. tropical winds (near the equator).

Where does a hurricane draw its energy?

• Latent heat stored in water vapor • released when water condenses • Warm water supplies sensible heat and humidity to overlying air • Air decreases density; rises • Air cools; H2O vapor condenses • Latent heat released • Heat warms air; rises faster • Pressure gradient increases • Faster winds converge at the low pressure center • More water vapor into system! • Feedback between the ocean and atmosphere systems!