Photon Phrightday: Pholcanoes

Narration: Jim Garvin


The death of an island is a common occurrence on our Earth.

And today ICESat-2, our satellite lidar

altimetry system, can see and watch these spectacular places.

It's almost spooky because islands are part of the glimmers

of how the Earth works in the giant oceanic environment.

So let's take a look at one of these island systems in a remote

part of the Southwest Pacific, known as the Kingdom of Tonga,

and this island archipelago is special because it has lots of volcanoes.

Recently, ICESat-2 was able to produce topography of one of these islands.

A recently formed one known as Hunga Tonga Hunga Ha'apai

in the Southwest Pacific and this island, only a couple

hundred hectares in extent, was burst from the shallow waters

oceans of this part of the Pacific about six years ago.

It constructed a 120-meter high volcano and that volcanic island's

been crumbling against the barrage of forces of the ocean

and tropical cyclones over the last six years.

ICESat-2 was able to see that island with the finest scale

precision of satellite laser altimetry possible

and show us the structure of the island as it's crumbling.

What ICESat-2 shows us the shallow crater lake that formed as the volcano

was erupting and then filled with ocean water is only ten or 15 meters deep.

It reflects what might be the volcanic vent system that led to the formation

of this special island.

Now, other islands in the Tonga system

haven't survived as well, and one erupted beautifully in the fall of 2019.

And that island, which is named

Late'iki, formed a new island just several meters above sea level

that was then witnessed by ICESat-2 a few months after the island washed away.

And what's left are the remnant shoals of a region that's very active.

The tip of a three kilometer, 10,000 foot undersea volcano

that pops its head above and below the waves every decade or two.

The death of islands is like the ghostlike relics of what the Earth once was.

And we know there's thousands of these things on the ocean

and the sea floor, most of which don't poke their heads above the water.