Announcements

• ANNOTATED VOLCANO: A VOLCANO'S SHAPE CAN TELL YOU HOW IT WILL ERUPT

  2018-09-12

  YOU GET A double feature for the latest Annotated Volcano. Why two volcanoes? I wanted to explain the difference between two different shapes of volcanoes: the archetype stratovolcano and the massive shield volcano. Why would two volcanoes take such different forms? It boils down to the flavor and form of the stuff that comes out the top.

  Stratovolcano

  Mexico's Popocatépetl is an example of what volcanologists call a stratovolcano*, with a well-formed conical shape and a crater/vent at the top of the volcano. You can see that shape in the profile shot of the volcano (taken from the Earth's surface; below) with steep slopes. The average slope heading up the sides of the volcano are ~25 percent with a maximum of 63 percent in the steepest bits. From the "base" level of ~3500 meters (11,400 feet) to the summit you gain 1635 meters (~5,300 feet). All in all, hiking this volcano would definitely be a slog, especially as you approach the summit and the slopes get even steeper. You can also notice a nearly circular shape to the volcano (above), with paths of debris heading in all directions from the summit crater.

  Read More Read more about ANNOTATED VOLCANO: A VOLCANO'S SHAPE CAN TELL YOU HOW IT WILL ERUPT

• NOBODY KNOWS WHERE THIS BIG RAFT OF PUMICE CAME FROM

  2018-09-12

  Last week, a Royal New Zealand Air Force flight spotted a new pumice raft in the middle of the Pacific ocean to the west of Tonga. Pumice rafts are floating islands of pumice created during a submarine volcanic eruption and they can persist for months or longer. This raft was seen by aircraft and satellite in an area with no known volcanoes. However, from the looks of the raft, it might be a long way from home. The pumice is strung out in long streamers, suggesting it has been smeared and distorted by ocean currents and weather as the pumice floats along the ocean surface.

  UPDATE: A number of people have asked a good question: how big is this raft? Based on the satellite images, it could be tens of kilometers long, but very narrow (hundreds to tens of meters?). It is a little tricky to get a confident size because of the resolution of the images.

  Read More Read more about NOBODY KNOWS WHERE THIS BIG RAFT OF PUMICE CAME FROM

• Smokey superlatives: widespread wildfire impacts seen from as far away as a million miles from Earth

  2018-09-12

  I was going to take a break from covering the wildfires blazing across large swaths of western North America — until I checked on remote sensing data this morning and saw the satellite imagery above and lower down in this post.

  In the the image above, captured by the Suomi-NPP satellite on Aug. 15, check out the thick, sandy-colored smudge of smoke blanketing a huge portion of western North America. At its greatest extents, I measure it at more than 1,000 miles west to east and 500 miles north to south.

  In British Columbia, 559 fires burning as of Wednesday prompted the Canadian provincial government to declare a province-wide state of emergency for the second year in a row.

  Read More Read more about Smokey superlatives: widespread wildfire impacts seen from as far away as a million miles from Earth