Some islands started in diamond-bearing regions under continents, geochemists say

The raw materials of some volcanic islands are shaped by some of the same processes that form diamonds deep under the continents, according to a new study. The study asserts that material from diamond-forming regions journeys nearly to Earth’s core and back up to form such islands, a process that could take two and a half billion years or longer — more than half of Earth’s entire history.
Geology News — ScienceDaily