11.   It was only then -- when an ocean current surrounded Antarctica and trapped cold air above it -- that the continent became cold enough to support an ice sheet.

12.   Loosen up the soil with a rake and lay a base of thick twigs, branches or brush to trap air at the bottom of the pile.

13.   Meanwhile, areas of freezing rain will develop east of the Cascades where shallow cold air is trapped in the valleys.

14.   Modern antilock brake systems are potentially difficult to bleed because air can be trapped in the high-pressure ABS pump and turn into froth.

15.   Sleet forms in winter storms when cold air is trapped below an advancing, rising warm air mass.

16.   Stationary bubbles indicate that the jelly was poured too slowly or from too great a height into the jars and air was trapped.

17.   That will trap the air and prevent it from circulating.

18.   That fluffed up the fur, which trapped more air in the spaces between the hairs, increasing the insulating effectiveness.

19.   The faucet might be sputtering because air is trapped in the pipes.

20.   The gap traps air and creates a barrier that absorbs and blocks sound so it cannot travel beyond the initial source.