Earth Science -Questions and Answers

Earth Science

Question 8

When you are at the beach, you notice that the waves seem to “break” at the same point as they come towards shore. Explain what is happening beneath the surface to cause the waves to break at this point

Moving closer to the shoreline, the depth of the water becomes shallower. As the waves move towards the sea, they begin to slow down owing to the shallow depth of water. The wave makes contact with the bottom of the ocean as the waters become shallower. As the waves move slowly, the wavelength or period becomes shorter. This increases the wave height. As the seafloor becomes steeper, the wave height becomes more pronounced. The part of the wave near the sea floor moves slowly as the crest increases speed. The bottom of the wave moves slowly because of increased friction with the sea floor. At some point, the crest of the wave overtakes the bottom, causing the water to break at a specific depth level. Waves therefore seem to “break” at the same point due to the reducing depth of the sea floor (Lutgens, Tarbuck, & Tasa, 2016).


Lutgens, F. K., Tarbuck, E. J., & Tasa, D. G. (2016). Foundations of earth science. New York, NY: Pearson Education.

Question 9

Discuss two reasons why summer temperatures in coastal locations in Southern California are cooler than coastal locations at the same latitude in Georgia

One of the reasons why coastal locations in Southern California remain cooler is the action of ocean currents. The costal locations in Southern California are swept by the California Current, which is part of North Pacific Gyre (this comprises of a large swirling current common in the northern pacific basin) (Cropper, Hanna, & Bigg, 2014). This current causes cold waters from northern pacific to move towards the Southern California coastline, and thus a cooling effect even during summers. Another reason why the costal locations remain cooler is upwelling. Upwelling occurs when cold ocean waters rise to the surface. This is caused by Coriolis effect that creates the Ekman spiral. Ekman spiral occurs when the surface of the ocean moves away due to the Coriolis Effect, causing waters at the bottom to rise (Cropper, Hanna, & Bigg, 2014).


Cropper, T. E., Hanna, E., & Bigg, G. R. (2014). Spatial and temporal seasonal trends in coastal upwelling off Northwest Africa. Deep-Sea Research, 86(1): 94 – 111.

Question 10

The best place to look for crabs is between the high tide and low tide zones (the tidal flat). Knowing this, would you expect to find more crabs during a full moon/new moon or during a quarter moon stage? Explain why

I would expect to find more crabs during the full moon. This is because during full moon, the gravitational effect of the moon and the sun combine to produce extreme tides. For instance, the high tides occur very high while the low tides occur very low (Beukema, Wolff, & Brouns, 1990). This means that one is likely to find more crabs during this time.


Beukema, J. J., Wolff, W. J., & Brouns, J. J. W. M. (1990). Expected Effects of Climatic Change on Marine Coastal Ecosystems. Dordrecht: Springer Netherlands.

Question 11

You are taking samples of water depth as you cross the ocean from North America to Africa. You notice that about halfway through your journey, the ocean floor is more elevated. Explain the plate tectonic processes that form this elevated region of the seafloor

The elevation between North America and Africa’s ocean floor is caused by subduction of the pacific plate under the North American plate. Plates moving close to one another cause subduction (Lutgens, Tarbuck, & Tasa, 2016). When the plates meet, one plate may move underneath the other within the subduction zone. Since one plate moves above the other, the surface becomes relatively raised.


Lutgens, F. K., Tarbuck, E. J., & Tasa, D. G. (2016). Foundations of earth science. New York, NY: Pearson Education.