We visited the petrified forest located on the western side of the island. It's a unique park, not only because of the petrified trees, but also because the trees are still in the same place where they were found. We were amazed at how clearly the wooden structure is visible.
Wikipedia says: The petrified forest was formed by successive volcanic eruptions which took place between 17 and 20 million years ago, covering a large part of the island in lava and ash.