EVS 124 midterm

Week 1: A Local System

• Identify elements of each earth system in a specific case: The Earth system consists of the atmosphere (air), hydrosphere (water), geosphere (land), and biosphere (living organisms). For example, in a forest, the atmosphere provides gases for photosynthesis, the hydrosphere provides water for trees, the geosphere provides nutrients from the soil, and the biosphere includes the trees, animals, and microorganisms that interact within the system.

• Identify interconnections between various earth systems: Earth systems are interconnected through the exchange of matter and energy. For instance, volcanic eruptions (geosphere) release gases into the atmosphere, which can affect climate patterns and influence the biosphere by impacting plant growth and animal habitats.

• Develop and interpret diagrams to visually represent these reservoirs and connections: These diagrams, sometimes called box models, illustrate how matter or energy is stored (reservoirs) and flows (connections) between different parts of the Earth system. The size of the boxes can represent the amount of material in each reservoir, while the arrows indicate the direction and magnitude of the flows.

• Describe how changes to one part of a system might affect other parts: A change in one Earth system component can trigger cascading effects throughout the entire system. Deforestation (biosphere) can lead to increased soil erosion (geosphere), altered rainfall patterns (hydrosphere), and changes in atmospheric carbon dioxide levels (atmosphere), impacting climate and other ecosystems.

Week 2: Seafloor Spreading

• Difference between continental shelf and shoreline; explain why one would expect continental shelves on opposite sides of an ocean to match better than shorelines: The shoreline is the dynamic boundary between land and sea, constantly shaped by erosion and deposition, while the continental shelf is the submerged, relatively flat extension of a continent. Continental shelves on opposite sides of an ocean are expected to match better because they represent a more stable, ancient geological feature that existed before the continents rifted apart, whereas shorelines are more recent and subject to localized changes.

• Be able to identify a fracture zone on a bathymetric map: Fracture zones are linear topographic features on the ocean floor, appearing as ridges and valleys that run perpendicular to mid-ocean ridges. On a bathymetric map, they are identifiable as long, narrow, and often irregular features that offset the otherwise linear pattern of the mid-ocean ridge.

• Be able to identify deepest/shallowest areas on bathymetric map: Bathymetric maps use contour lines or color gradients to represent ocean depth; the closer the contour lines, the steeper the slope. The deepest areas are indicated by the highest contour values or specific color codes (typically darker blues), while the shallowest areas (like continental shelves or seamounts) have lower contour values or different color codes (lighter blues, greens, or yellows).

• Locate newest and oldest ocean crust based on location of mid-ocean ridge: The newest oceanic crust is found at the mid-ocean ridges, where magma upwells and solidifies, creating new seafloor. The oldest oceanic crust is located farthest away from the mid-ocean ridges, near the continental margins or subduction zones, as it has been moving away from the ridge since its formation.

• Calculate rate of seafloor spreading based on age of crust: The rate of seafloor spreading is calculated by dividing the distance of a specific point of the ocean crust from the mid-ocean ridge by its age. This calculation provides the average speed at which the oceanic crust moves away from the ridge over millions of years, usually expressed in millimeters per year (mm/yr) or centimeters per year (cm/yr).

• Explain source of magnetic stripes, explain why they are symmetric about mid-ocean ridge: Magnetic stripes are formed due to the periodic reversals of Earth's magnetic field. As magma solidifies at the mid-ocean ridge, magnetic minerals align with the Earth's magnetic field at that time, creating a record of its polarity. These stripes are symmetric about the mid-ocean ridge because new crust is continuously formed and pushed away equally on both sides, recording the magnetic field reversals in a mirrored pattern.

• Given a magnetic profile, determine rate of seafloor spreading: By analyzing a magnetic profile, you can identify the distance between magnetic stripes that represent specific magnetic reversals with known ages. Dividing the distance between two corresponding magnetic stripes on either side of the mid-ocean ridge by the time difference between the reversals gives you the rate of seafloor spreading.

Week 3: Earthquakes

• Be able to describe distribution of earthquakes, any anomalous locations: Earthquakes are not randomly distributed; they primarily occur along plate boundaries, such as the Pacific Ring of Fire, mid-ocean ridges, and collision zones like the Himalayas. Anomalous locations, such as intraplate earthquakes (e.g., New Madrid Seismic Zone in the central US), occur within the interior of tectonic plates and are less understood.

• Know what types of information are available about earthquakes on http://earthquake.usgs.gov/: The USGS website provides real-time and historical data on earthquakes, including location, magnitude, depth, time of occurrence, maps, ShakeMaps, and information on potential impacts and aftershocks. You can also find scientific information, educational resources, and tools for searching and analyzing earthquake data.

• Describe what information is provided with the Historical Seismicity overlay: The Historical Seismicity overlay provides information on past earthquakes, including their location, magnitude, and date of occurrence. This data helps identify patterns, assess seismic hazards, and understand the long-term earthquake history of a region.

• Explain difference between ShakeMap intensity and magnitude: Earthquake magnitude is a quantitative measure of the energy released at the earthquake's source, usually reported on the Richter scale or moment magnitude scale. ShakeMap intensity, on the other hand, is a qualitative measure of the ground shaking and damage caused by an earthquake at a specific location, based on observed effects on people, buildings, and the environment, and is reported using the Modified Mercalli Intensity Scale.

• Use difference in arrival times of P and S wave to determine epicenter of an earthquake: P-waves (primary waves) travel faster than S-waves (secondary waves). The greater the difference in arrival times between P- and S-waves at a seismograph station, the farther away the earthquake epicenter is from that station. By using data from at least three seismograph stations, a process called triangulation can pinpoint the earthquake's epicenter.

Week 4: Seasons

• Explain differences between flat map and globe representations of the earth, including how size distortions arise: Flat maps inevitably distort the Earth's surface because they attempt to represent a three-dimensional object in two dimensions. This distortion can affect the shape, area, distance, or direction of features, whereas globes accurately represent the Earth's shape and spatial relationships, but are less convenient for showing detailed information.

• Understand definitions of latitude and longitude: Latitude measures the angular distance, in degrees, north or south of the Equator, which is 0° latitude, with the poles at 90° N and 90° S. Longitude measures the angular distance, in degrees, east or west of the Prime Meridian (Greenwich, UK), which is 0° longitude, ranging to 180° E and 180° W.

• Describe where the sun is most and least direct in the summer and winter, and where beam spreading is greatest: During the summer solstice in the Northern Hemisphere, the sun is most direct at the Tropic of Cancer (23.5° N), while during the winter solstice, it is most direct at the Tropic of Capricorn (23.5° S). Beam spreading, the distribution of sunlight over a larger area, is greatest at higher latitudes (near the poles) where the sun's angle is more oblique.

• Describe what make the tropics special in terms of sunlight? The tropics, the region between the Tropic of Cancer and the Tropic of Capricorn, are unique because they are the only areas on Earth where the sun can be directly overhead (at a 90-degree angle) at solar noon. This results in consistently high levels of solar radiation and relatively small seasonal variations in temperature.

• Describe what make the polar regions special in terms of sunlight? The polar regions (Arctic and Antarctic) experience extreme variations in sunlight throughout the year, including periods of 24-hour daylight in the summer and 24-hour darkness in the winter. This is due to the Earth's axial tilt, which causes these regions to be tilted either towards or away from the sun for extended periods.

• Describe which regions of the earth can have days with no sunlight, and explain why this occurs: Regions within the Arctic and Antarctic Circles can experience days with no sunlight during their respective winter seasons. This occurs because the Earth's axial tilt causes these regions to be completely in shadow as the Earth rotates.

• Describe how the extent of seasonal variations depends on latitude (at which latitudes are seasonal variations greatest? Least?) and explain why: Seasonal variations in temperature and sunlight are greatest at higher latitudes (near the poles) and least near the equator. This is because the angle of sunlight and the length of day vary more dramatically at higher latitudes throughout the year due to the Earth's axial tilt.

• Relate seasonal temperature variations at a given latitude to directness of sunlight and hours of sunlight: Seasonal temperature variations are closely related to the directness and duration of sunlight. When sunlight is more direct and the days are longer (summer), temperatures are higher because the Earth's surface receives more solar energy. Conversely, when sunlight is less direct and the days are shorter (winter), temperatures are lower due to reduced solar energy input.

Week 5: Atmospheric Composition and Structure

• Calculate speed of air molecules: The speed of air molecules can be calculated using the kinetic theory of gases, which relates the average kinetic energy of gas molecules to temperature. The root-mean-square speed (vrms) is calculated using the formula vrms = √(3RT/M), where R is the ideal gas constant, T is the temperature in Kelvin, and M is the molar mass of the gas.

• Explain why Earth’s atmosphere does not contain hydrogen: While hydrogen is the most abundant element in the universe, it is very light, and at Earth's temperatures, hydrogen molecules move at speeds exceeding Earth's escape velocity. This allows hydrogen to escape into space, preventing it from accumulating in the atmosphere.

• Describe and explain relationship between surface temperature and the lowest temperature in the vertical profile: Typically, surface temperature is the warmest, and temperature decreases with altitude in the troposphere. The lowest temperature in the vertical profile is usually found at the tropopause because this is where the troposphere (heated from below) transitions to the stratosphere, which is heated from above by ozone absorption of UV radiation.

• From a vertical profile, determine location of tropopause, areas of inversion: The tropopause is identified on a vertical temperature profile as the boundary where the temperature stops decreasing with height and begins to increase or remains constant. Areas of inversion are regions where temperature increases with altitude, rather than decreases, and can be identified as upward-sloping segments on the temperature profile.

• Describe trends in wind speed (are strongest winds at the surface, or not?) Wind speeds generally increase with altitude in the lower atmosphere. Surface winds are typically slower due to friction with the Earth's surface, which slows down the air.

• Describe trends in height of tropopause wrt latitude: The height of the tropopause is generally higher at the equator and lower at the poles. This is due to the greater thermal expansion of the atmosphere at the equator, which causes the troposphere to be thicker in the tropics.

• Describe trends in height of tropopause wrt season: The tropopause height varies with the seasons, generally being higher in the summer and lower in the winter. This is related to the seasonal changes in temperature and the expansion/contraction of the troposphere.

• Relate height of tropopause to lowest temperature in vertical profile: A higher tropopause generally corresponds to a lower (colder) temperature at the tropopause. This is because as the air rises and expands (resulting in a higher tropopause), it cools adiabatically, leading to lower temperatures at that altitude.