A thick layer, or seam, of coal tells us that the ancient forest swamp existed for a remarkable length of time.
(A thick layer, or seam; tells; us; that the ancient forest swamp existed for a remarkable length of time) Context(A thick layer , or seam tells,List([0, 37))):(the ancient forest swamp; existed; T:for a remarkable length of time)
A thick layer , or seam tells,List([0, 37))
A thick layer, or seam the ancient forest swamp
tells existed
us that the ancient forest swamp existed for a remarkable length of time
T:for a remarkable length of time