It is a matter of debate as to whether Helston was once a port, albeit no actual records exist. A common belief is that in the 13th century Loe Bar formed a barrier across the mouth of the River Cober cutting the town off from the sea. Geomorphologists believe the bar was most likely formed by rising sea levels, after the last ice age, blocking the river and creating a barrier beach. The beach is formed mostly of flint and the nearest source is found offshore under the drowned terraces of the former river that flowed between England and France, and now under the English Channel.