Fall begins at exactly 6:49 a.m. EDT on Sept. 22.

These glaciers are smaller than Antarctica's, but more dangerous to ships.

Arctic sea ice recedes as summer begins.

Clear skies reveal Rockies, Cascades and other features of the western landscape.

Bogana volcano is almost constantly active but its remoteness makes it hard to monitor.

Etosha Pan in Namibia rarely receives the water that flows down its tributaries.

Satellites see greening of trees.

Eddy currents push around small icebergs.

Computer models, buoys track its progress.

Watch this amazing animation of equinoxes and solstices from space.

Investors want to float shipwreck back to Norway.

Blues and greens explode.

Acidic oceans could be bad news for marine life.

Ice chunk broke off of Greenland glacier nearly one year ago.

Second leg of voyage to study changing waters of the Arctic Ocean.

Melt ponds add variation to stretches of sea ice.

Updated charts needed as sea ice loss drives increase in ship traffic.

Iceberg has traveled nearly 2,000 miles in Arctic waters.

Still not even close to the biggest tsunami ever.

The wave swept ashore, surprising holidaymakers and fishermen alike.

Second leg of the mission begins June 25.

Unusually thick, strong sediments allowed quake to move more seafloor.

Caves carved by water over eons.

Ocean waters, debris overflowed river and inundated croplands.