Just offshore, the ocean's bottom forms an incredible system of underwater canyons. Unlike the nation's Eastern Seaboard, the California coast lacks the shallow ledge of the Continental Shelf. Instead, the offshore bottom plunges steeply to over a mile in depth! Underwater mudslides race through these canyons, cutting paths into this unseen seascape. Within these waters, all sorts of bizarre deep-ocean animals and communities can be observed.
Minor earthquakes can set in motion unstable mud. This moving mud produces a mudslide that flows along the natural cut of the submarine canyon. Within this turbid flow, a variety of coast pollutants and sediments can be carried miles offshore into the deeper cuts of the canyon. In this activity, you’ll get the opportunity to model this event.
1. Examine the illustration on page 88. Note how the color depth key can be used to interpret the topography of the sea bottom. Identify the canyons, plains and hill-like features of this underwater scene.
2. In a small bowl, construct a model of this underwater landscape. Make sure to sculpt out the major cuts illustrated in this diagram. Use a different color clay to represent the dry land of the California coast.
3. Add water to the bowl to submerge the underwater topography.
4. Fill a cup half full of water. Add several teaspoons of salt. Stir to dissolve the salt. Add several drops of food coloring. Mix well.
5. Slowly pour the dyed saltwater solution into the bowl. This thin stream should enter the bowl just above the mouth of the sculpted major canyon. Observe its movement. What do you see? Does the poured water mix with the water already in the bowl? Explain.