The dark colored lunar plains that we can see from earth are called Maria. This comes from the Latin word "mare" (plural: maria ) meaning sea. This came about because ancient astronomers thought that they were filled with water. It is now established that these are large pools of solidified basaltic lava.
These seas are found mostly on the near side of the moon which is the one facing us. Many of them have been named as they were mapped and some of these are described below.
Photo: Wikipedia Commons
Sea of Cold
The Sea of Cold, or Mare Frigoris is at the top of the moon. It is situated to the east of the Lunar Alps. The dark portion at the bottom left of the photograph shows its location.
Sea of Tranquility
Mare Tranquillitatis is where visitors from earth first set foot on the moon. The Apollo 11 landing site is here.
Ocean of Storms
Oceanus Procollarum is a large lunar sea on the western edge of the nearside of the moon. It is the largest lunar sea and measures more that 2,500 kilometres in length from north to south. It can be seen at the center towards the upper-left of the photograph.
Sea of Moisture
Mare Humorum, or Sea of Moisture, is 389 kilometres in diameter. It is on the southwest of the near side of the moon.
Sea of Clouds
Mare Nubium, or the Sea of Clouds is situated to the south-east of Oceanus Procollarum.
Sea of Fertility
The Sea of Fertility, or Mare Fecunditatis is 909 kilometres across. It is situated in the middle of the eastern side of the moon (near side) on what would be the equatorial line on earth.
