The Mariana Islands consist of a chain of volcanic islands approximately 450 miles long. As shown in figure 2, there are 14 single islands and one group of three islands (Maug), from Uracas in the north to Guam in the south. The Palau Islands which are situated in the easternmost part of Micronesia have often been considered from a political standpoint as part of the Caroline Islands. As shown in figure 3, the Palau Islands are a chain of islands approximately 120 miles long from north to south. Sonsorol, Tobi, Merir, Pulo Anna, and Helen Island occur to the southward of the Palaus and may be considered as part of the Carolines or as part of the Palaus. The Palaus together with the Carolines, to the eastward, extend in an east-west direction for approximately 1,700 miles. The Palaus and Carolines include (as shown in figures 3 and 4) 37 atolls, 34 banks, 11 coral islands without lagoons, 2 uplifted phosphate islands, 4 volcanic islands, and the Palau chain. The Marshall Islands to the extreme eastward extend approximately 700 miles from north to south and, as shown in figure 5, contain 29 atolls and five coral islands without lagoons. No volcanic exposures occur in the Marshall Islands. There is a total land surface of approximately 846 square miles in the islands of Micronesia. The Palaus and Carolines have 525 square miles, the Marianas 247 square miles, and the Marshalls 74 square miles of land surface. Guam has the largest land surface of any of the islands of Micronesia with 225 square miles, Ponapé has 145 square miles, and Babelthuap has 143 square miles. Asuncion, in the northern Marianas, has the highest elevation, rising as an almost perfect cone to a height of 2,923 feet; Ponapé reaches a height of 2,579 feet above the sea level. The volcanic islands are known as "high" islands, and the coral atolls are known as "low" islands. The coral islands usually rise but a few feet above sea level. CLIMATE In Micronesia there are two seasons: a wet summer and a dryer winter. Temperatures rarely go above 90° F. and rarely below 70° F. Rainfall in the Marianas averages approximately 85 inches per year, in the Palaus approximately 150 inches, in the Carolines it ranges from 129 to 185 inches, and in the Marshalls it goes up to 160 inches. The humidity is excessive, the average annual mean of relative humidity for selected islands in Micronesia being between 82 and 86 percent. The relative humidity is lower in the western Carolines and the Palaus, than in other parts of Micronesia.