The left half is bare earth: a LiDAR survey with the vegetation stripped out, so you are looking at the ground itself rather than the canopy over it. That is why old roadbeds, homesteads, quarries, railroad grades and sinkholes show up here and vanish on the aerial side. Elevation comes from the USGS 3D Elevation Program at up to one metre; coverage and detail vary by county, and the oldest surveys are coarser. Drag the handle, or focus it and use the arrow keys.