It is most likely a compound "kettle" lake, formed by several large ice blocks that broke off a retreating glacier and eventually melted, leaving several, joined depressions in the surrounding landscape of what was once a pre-glacial valley.
(It; is most likely; a compound "kettle" lake, formed by several large ice blocks that broke off a retreating glacier and eventually melted, leaving several, joined depressions in the surrounding landscape of what was once a pre-glacial valley) (a compound "kettle" lake, formed by several large ice blocks; leaving; several, joined depressions) (several large ice blocks; broke off; a retreating glacier) (several large ice blocks; melted; T:eventually)
It a compound "kettle" lake, formed by several large ice blocks several large ice blocks several large ice blocks
is most likely leaving broke off melted
a compound "kettle" lake, formed by several large ice blocks that broke off a retreating glacier and eventually melted, leaving several, joined depressions in the surrounding landscape of what was once a pre-glacial valley
several, joined depressions
a retreating glacier
T:eventually