Anacapa separated first, roughly 10,300 to 10,900 years ago.

The other islands followed as the low saddles connecting them were overtopped by the rising sea.

By roughly 10,000 years ago, the four modern northern Channel Islands were distinct, separated by water.

This process was, in geological terms, rapid.

In human terms, it unfolded over many generations — slowly enough that no individual experienced it as a cataclysm, but fast enough that it was visible within a lifetime.

The people who lived through this transformation watched their island shrink and divide.