Students will create a two-dimensional contour map of a submerged area from a simulated survey using sounding techniques. Two students per group. In the activity Building a Topographic Model, students created a three-dimensional model of a landform above sea level. We now know that mountain ranges and canyons on the ocean floor are as spectacular as any on land. Even though they are covered by water, these landforms can be shown on maps like those showing their terrestrial counterparts, and most students have probably seen the National Geographic's maps of the ocean floors.
Bathymetric maps are topographic maps of landforms that are submerged beneath the ocean or a lake.
Mapping the bottom of a body of water presents some special problems because the bottom is not visible. Several techniques are currently used to collect depth data for mapping. When mapping a small, shallow lake it is possible to go out and measure the depth of selected locations with a weight tied to a rope which is lowered over the side of the boat. A long pole can also be marked with depth intervals and used to make soundings. To collect depth data, one must systematically row the boat around the lake and lower the rope over the side of the boat or drop the stick until it reaches the bottom.