Answer :
The main focus of the text is:
- What the mid-ocean ridge system is like
The text describes the mid-ocean ridge system as the most extensive chain of mountains on Earth, even though it is not as well-known as other mountain ranges like the Himalayas or the Andes. It highlights that more than ninety percent of the mid-ocean ridge system is located underwater. The system stretches for an impressive 65,000 kilometers around the globe.
In summary, the text's main focus is to describe the mid-ocean ridge system, its vastness, and its unique location predominantly under the ocean. It aims to introduce readers to this significant geological feature that plays a crucial role in shaping the Earth's surface.