Ancient glaciers eroded many of the valleys, creating space for the lakes as they melted at the end of the last Ice Age, approximately 8,000 b.c.
The last ice age ended approximately 10,000 years ago.
With these proofs of conspiracy in their hands, aided further by a small brown diary taken from the pocket of the dead man which had contained a full and damning resume of the whole plot, the Government had called an eleventh-hour conference.