Scientists have estimated that over 100 years Periwinkles may remove as much as two and a half inches of rock.
(Scientists; have estimated; that over 100 years Periwinkles may remove as much as two and a half inches of rock) Context(Scientists have estimated,List([0, 25))):(over 100 years Periwinkles; may remove; as much as two and a half inches of rock)
Scientists have estimated,List([0, 25))
Scientists over 100 years Periwinkles
have estimated may remove
that over 100 years Periwinkles may remove as much as two and a half inches of rock
as much as two and a half inches of rock