For Christmas, my friend Alison gave me the 1928 Popular Science Monthly “Pocket Guide to Science.” It’s a treasure, including things like this:
What produced the Grand Canyon of Arizona?
It was cut down, during millions of years, by the Colorado River which still flows in the bottom of it. The sand and clay cut out of the Grand Canyon was carried down into the Gulf of California. It has made the flat, muddy plain part of which is now the famous Imperial Valley of California.
The Imperial Valley was famous in 1928? Good to know.
To be fair, there were some things we understand today that hadn’t been quite worked at in 1928:
Why do we believe that the earth may be slowly shrinking?
That is one theory of how mountain ranges are formed. As the earth shrinks it wrinkles up its surface skin a little, some geologists believe, just as the skin of a prune wrinkles up when it dries and shrinks. These wrinkles on the earth are what we call mountains. It is possible, however, that mountains can be formed in other ways also.