Is the underlined word 'warning' a noun or a verb? Thank you in advance for your help.
Non-geologists are usually not aware that the very existence of a cliff is warning that erosional processes are at work, even though the changes seem to be very slow.
It's a noun. (Not relevant to your question, but the statement doesn't seem very plausible to me. )
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
It's a noun.
(Not relevant to your question, but the statement doesn't seem very plausible to me. I would have thought most people would realise that cliffs are associated with erosion.)