This map shows how the terrain may have appeared during the Last Glacial Maximum, around 21,000 years ago, when sea levels were approximately 125 meters (410 feet) below present. This map does not include any lakes of this time period. The coloring of the map is based on height and is not meant to represent the climate or vegetation in any way. You can find the elevation key as a separate image here. This map has some noticeable lines running in different directions across the landscape that appear as ridges or trenches. These in most cases are more than likely to be an issue caused by merging different quality datasets. The sonar scanning that was used to map the seabed will pick up higher accuracy readings of depth along the path that the ships travel, and when merged with lower quality height data of the surrounding areas, will appear to stand out.
Reddit user : v7x