Some propose storing the CO2 in coal mines or liquid storage in the ocean, Shell favors storing CO2 in deep geological structures such as saline(鹽的) formations and exhausted oil and gas fields that exist throughout the world.

In geological time, a million years is recent history.

By explaining some essential geological principles.

As he prepared the speech, Juan kept asking himself, "How can I make this clear and meaningful to someone who knows nothing about earthquakes or geological principles

The hills are remnants of an earlier geological era, scraped bare of most soil and exposed to the elements.