1.   Another sign of buildup is an audible gurgling or rumbling sound caused by air bubbles rising through the sediment layer to the water above.

2.   Augmenting the SeaBearn map is a readout that gives a cross section of the sediment layers below the seafloor.

3.   A few dozens of millions of years passed, seaways became lakes and the sediment layers kept building up, muck upon muck.

4.   In cross section the sediment layers have a characteristic wavy pattern.

5.   Priscu and his team found the microbes after years of drilling through the sediment layer.

6.   The thickness of the annual sediment layers in the cores reflects how fast the ice sheet was melting.