Why do mass extinctions occur and why do they often mark divisions of geologic time?

Poling our way along the inky green waterway, we glided upstream through quiet still-water bends in the river, where mats of fragrant white flowers had gathered, closing behind the stern of our 24-inch-wide dugout and concealing any sign of our passage. —eric hansen, stranger in the forest: on foot across borneo, 1998 which of these items in the passage is an example of borneo’s flora? a. “the inky green waterway” c. “mats of fragrant white flowers” b. “still-water bends in the river” d. “the stern of our 24-inch-wide dugout”