Introduction

Accurate base maps are a prerequisite for any geological study, regardless of the objectives. Land-based studies commonly utilize aerial photographs, USGS 7.5-minute quadrangle maps, and satellite images as base maps. Until now, studies that involve the ocean floor have been at a disadvantage due to an almost complete lack of accurate marine base maps. Many base maps of the sea floor have been constructed over the past century but with a wide range in navigational and depth accuracies.

Only in the past few years has marine navigational accuracy approached 1 m and depth resolution 50 cm. State-of-the-art digital multibeam systems are used to systematically map the seafloor. The two types of data collected include bathymetry (seafloor depth) and backscatter (data that can provide insight into the geologic makeup of the seafloor). These data are of critical importance to groups as diverse as marine habitat biologists, state and local authorities setting regulations on seafloor uses, school children, and teachers. The new high-resolution base maps will be used for:

• identifying areas of erosion and deposition on the continental shelf
• locating areas of geohazards (such as slumps and faults)
• locating pathways for movement of sediment and pollutants

Ongoing research is attempting to derive better relationships between the backscatter collected from a multibeam mapping system and the seafloor geology. The ultimate goal of this research is to convert the backscatter maps into geologic maps.