What, How, Why The Sea

Earth is largely covered by water: oceans, lakes, and rivers make up 71% of the Earth's surface, which explains why, when we look at our planet from space, we see it as a large blue ball. When did oceans and seas form? What's the difference between a sea and an ocean? What organisms live in the marine ecosystem? This book from the "What, How, Why" series explores various aspects of seas and oceans, a fundamental resource for life on Earth, using a question-and-answer format.