Volcanic Islands, Blue Lagoons, and Coral Reefs

The French Polynesian islands that we visited last week are all very new, compared to the solid continents where most humans live. Like the Hawaiian islands, these islands are a chain that formed one by one, passing over a deep volcanic hotspot. Thus each island began as a shield volcano in a very deep part of the Pacific Ocean.

Everything about the islands reflects their recent volcanic formation: their shape, their rugged peaks, the sandy beaches with coral reefs and lagoons surrounding them, and the contrasting colors of deep blue water or shallower pale blue water where white sand is beneath the sea. For example, the silhouette of the island of Moorea, seen from Tahiti, is very rugged.

A white sand sea floor causes the water above to look bright turquoise.
The white sand is made from coral, which grows on reefs surrounding
the new volcanic islands. Tropical fish bite off bits of coral and grind it
in their digestive system, slowly creating the coral sand.

Somewhat older islands have a very different form: that of an atoll where the original volcanic peak has sunk into the sea, and ultimately the fringing reef forms a chain of islands around a blue lagoon.

Entering a lagoon -- a risky passage because the water is flowing quickly and
kicking up turbulent waves.

Atolls appear to be chains of small islands, which can often go on for miles.

Rarely, a sunken atoll is uplifted from the sea floor by geological conditions.
We visited the island of Makatea, which was formed this way.

Below the ocean's surface off shore are coral reefs. These include an incredible variety of undersea life, including fish, sharks, coral of all shapes, sponges, invertebrates like worms, clams with colorful mantles, and much much more. Polynesian islands are fantastic locations for snorkeling or diving. We snorkeled every day of our trip on the National Geographic Orion last week; on the last day of the trip, we skipped a trip to see the cultivation of the very famous black pearls in favor of a second time snorkeling.

Here are a few of Len's photos of our snorkeling experiences:

As I swam from the snorkeling platform, shoals of fish greeted me. An amazing experience!

It's always fun to see a shark!

The mantle of each clam (that is, the soft part that you see in its wavy shell opening) varies in color because of algae that
live symbiotically with the clam. I loved seeing them, half-buried in the coral heads.

The very colorful worms poke their lacy feeding structures out of the coral. When frightened, they pull back into their holes.