A topographic map of Mount Rainer. Index contour lines are 13,600, 13,800, and 14,000. There are 4 contour lines between each index contour. A red triangle labeled Columbia Crest has number 14,410 next to it. Use the drop-down menus to answer each question about the topographic map.

uses contour lines to show elevations and shapes of landforms ... written on each index contour line ... find the difference in elevation between the index contours ... contour line has the same elevation as the lowest contour line that is next to it ... will be marked on the map by a "x", or a triangle, and the elevation for that spot.

answer; (d) melting of sea ice;