The quadrangle lies at the center of the Puget Sound region's intensively developing urban core. Only a few km north lies the city of Seattle, about 20 km south is the city of Tacoma, and Seattle-Tacoma International Airport lies near the center of the quadrangle, perched high in the center of the upland plain. The map area expresses much of the tremendous range of Quaternary environments and deposits found throughout the central Puget Lowland. Much of the ground surface is mantled by a rolling surface of glacial till deposited during the last occupation of the Puget Lowland by a great continental ice sheet about 14,000 years ago. A complex sequence of older unconsolidated sediments extends far below sea level across most of the quadrangle; bedrock is exposed only in the extreme northeast corner of the quadrangle.