Yes, as from outer space earth appears blue because over 71 percent of it is covered with water so Earth is called the 'Blue Planet'.
How long ago was the earth formed?
The earth formed about 4.6 billion years ago.
Define Sial and Sima?
The continents are composed of lighter silicate, silica + aluminium is called Sial. The oceans have the heavier silicates, silica + magnesium is called Sima.