Isohalines are lines joining equal:

The correct answer is salinity.

Key Points

• Isohalines
  • It is used on maps to show the salinity of different places. Hence, Option 4 is correct.
  • The average salinity of the ocean is 3.5% or 35 parts of salt in 1000 parts of water.
  • The salinity of the Great Salt Lake, (Utah, USA), the Dead Sea, and the Lake Van in Turkey are 220, 240, and 330 respectively.
  • The oceans and salt lakes are becoming saltier as time goes on because the rivers dump more salt into them, while freshwater is lost due to evaporation.
• The more frequently drawn isopleths include:
  • Isotherm (equal temperature)
  • Isobar (equal pressure)
  • Isohyets (equal rainfall)
  • Isonephs (equal cloudiness)
  • Isohels (equal sunshine)
  • contours (equal heights)
  • Isobaths (equal depths)