What are Braxton Hicks contractions? Braxton Hicks contractions can begin as early as the second trimester. However, they are most commonly experienced in the third trimester. When this happens, the muscles of the uterus tighten for approximately 30 to 60 seconds, and sometimes as long as two minutes.
Main articles: Hydrology and Water distribution on Earth. Water covers 71% of the Earth's surface; the oceans contain 96.5% of the Earth's water. The Antarctic ice sheet, which contains 61% of all fresh water on Earth, is visible at the bottom. Condensed atmospheric water can be seen as clouds, contributing to the Earth's albedo.
Even though the planet is 71 percent water, the largest percentage of Earth's water is saltwater in the oceans and cannot be used for drinking. The table describes the main locations of water on Earth. Notice that about 98 percent of Earth's water is saltwater. The remaining 2 percent is freshwater, but the majority of that percentage is found in the polar ice caps and glaciers, which is not readily available to us.