What is lake turnover and why does it occur?

Question

What is lake turnover and why does it occur?

Answer 1

Lake turnover occurs when the different layers of water reach the same temperature.  This causes the water at both levels to mix.  As the summer goes on the water on the surface warms and the lower levels remain cool forming new layers again.  In the fall the upper layer will cool and the mixing will occur again.

Answer 2

lake turover occurs when seasons change

why

don't remeber.....