Chapter 1: Answers to Study Problems
1. Because the longitudes of the two points are the same, the distance between the points is based on the change in latitude only. Students need to recall that 1° of latitude equals 60 nautical miles and that 1° of latitude is divided into 60 minutes.
45.0° N - 38.5° N = 6.5° of latitude,
6.5° * 60 nm/° latitude = 390 nm,
1 km = .540 nm; therefore, 1 nm = 1.85 km and 390 nm = 721.5 km.

Chapter 1: Answers to Study Questions
3. The answer should consider the Earth's distance from the sun, the presence and composition of its atmosphere, its rotation rate, its orbital period, and the relative length of its solar day compared with other planets.

15. The ocean's areas between 4,000– and 5,000–m depth is the largest (see fig. 1.23).

Chapter 2: Answers to Study Questions

8. At the time Alfred Wegener proposed the drifting of the continents, no mechanism to account for the movement was known. The discovery of the midocean ridge systems, the accumulation of knowledge from new instruments, and research techniques developed during World War II prepared the way for the development of the convection cell theory of crustal movement. Data from the dating of crustal material, magnetic surveys of the seafloor, polar wandering, and deep-sea coring and heat-flow sampling used sophisticated instrumentation and produced the data for the reinterpretation of earth processes.

11. If the subduction zone is at the edge of a plate bearing continental material, the continental crustal material can be crumpled up, forming elevated mountain masses (for example, the Chilean Andes). When the subduction zone occurs away from landmasses, the crustal material that is carried down into the mantle becomes molten and moves toward the surface through fractures along the subduction zone to produce explosive andesite volcanoes and island arcs (for example, the Aleutian Islands and Mount St. Helens). The magmatic material of such volcanoes is explosive because of its high water and gas content.

12. Students should be encouraged to recognize the overlap of earthquake belts with plate boundaries. Midocean ridges and rises, major transform faults, and trenches should be included and conclusions drawn about their relationships.

Chapter 2: Answers to Study Problems

1. Displacement equals rate of displacement times time:
(5 cm/year) * 180 * 106 years = 900 * 106 cm
900 * 106 cm = 9 * 103 km.

2. The average displacement of the magnetic stripes from the ridge crest is
(9 km + 11 km) / 2 = 10 km.
Average spreading rate for each side is displacement divided by age of the stripe:
10 km / (4 * 105 years) = 2.5 * 10-5 km/year = 2.5 cm/year.

Chapter 3: Answers to Study Questions

1. A large area of the South Pacific Ocean has an extensive rise system that produces the
shallow depths that allow calcareous organic remains to accumulate and form calcareous
oozes at depths of less than 2500 m. In the North Pacific, the lack of a major rise or ridge
system produces depths greater than 1000 m, and the calcareous remains dissolve rather
than accumulate. The South Pacific is saturated with calcite (0–2500 m), while the North
Pacific is saturated only through its first 500 m.

3. The four basic sediment types, classified by source, are:
         1. lithogenous—formed from rock that is exposed to erosion, often terrigenous
         (from land);
         2. biogenous—derived from the remains of living organisms;
         3. hydrogenous—chemically precipitated from water;
         4. cosmogenous—from extraterrestrial debris.
Lithogenous sediments are usually found close to land sources. Very fine lithogenous
sediments (red clay) are found in midocean if other sediment sources are very small.
Biogenous sediments, derived from coral and shell, are found in shallow water. In
midocean areas, biogenous oozes are present where organisms producing hard remains
are abundant in the overlying surface water.
Hydrogenous sediments precipitated from seawater are found in nearshore or midocean
environments where other sediment types accumulate slowly. Hydrogenous sediments are
often associated with red clay areas where sediments form slowly; they also form where
currents do not allow the accumulation of fine particulate material.
Cosmogenous sediments are not very abundant and accumulate slowly; therefore, they
are generally evident when other sediments accumulate slowly. If cosmogenous bodies
melt and disintegrate as they strike the Earth, the cosmic particles are laid down in a
splash pattern.

6. Submarine canyons are thought to be eroded into the continental shelf and slopes by turbidity currents or downward moving shelf sediments. Their appearance on the shelf may be related to river scour during previous periods of low sea level. Faults at the edges of continents may also help form these canyons.

7. The continental margin is made up of the continental shelf, continental shelf break, continental slope, and continental rise. Deposit patterns on the continental shelf are outwash deltaic materials from land sources, wave eroded coastal materials, shallow water biogenous deposits from reef-building mollusks and corals in warm water, and planktonic remains from the local overlying water column. Materials may be redistributed by currents. Coarser land-derived materials are deposited nearshore, finer materials offshore. Deposits on the continental slopes may be thin due to slope steepness. Layered turbidities may be found in the lower portion of a slope or on the rise where turbidity currents flowing down slopes deposit their slurries of coarse particles that are
overlaid by finer particles in a bedded structure known as a turbidite.

13. Sediment particle size distribution is used to identify turbidities, to relate sediments back to their sources, to define the transport processes that have influenced size sorting (stronger currents winnow out a larger range of fine sediments leaving only the coarser fractions behind). Particle size can describe the vertical and horizontal extent of areas having similar sediment characteristics. Once a sediment has been described, future comparative sampling will reveal any changes and may suggest the processes at work to modify sediment distribution.

Chapter 3: Answers to Study Problems

1. If the breaking of the cables is controlled by a moving flow such as a turbidity current, the downslope speed of the current is approximated by:
14 km/15 min = 0.933 km/min = 15.55 m/sec.