Contemporary occasions in Hawaii had been generating some remarkable images. But if you’re not a geologist—or resident of Hawaii—you might be wondering what the heck is going on. We’re here to help: while lava spewing from back yards in a subdivision seems wild, it’s not really surprising.
Why is Kīlauea an active volcano in the first place?
The Hawaiian chain of islands (there are also seamounts that no longer reach above sea level) is the result of a “hotspot” in the Earth’s mantle. Hotspots in the Earth’s interior are areas of rising hot rock that can turn to liquid hot magma near the Earth’s surface. These hotspots are basically stationary, while tectonic plates slowly slide around on the surface. That means a hotspot will punch a line of eruptions through the plate a bit like a sewing machine.
The Big Island of Hawaii is the youngest in the chain, still straddling the hotspot that fuels its volcanoes—there are five individual volcanoes that make up the island. Of those five, Kīlauea is the youngest, comprising the southeastern edge of the island. Kīlauea’s summit is home to a collapsed crater called Halemaʻumaʻu Crater. In 2008, a new vent appeared in the floor of the crater, which has hosted a lake of roiling lava ever since.
Volcanic activity also takes place along a straight southwest-northeast line known as the East Rift Zone. In 1983, eruptions produced Pu‘u ‘Ō‘ō Crater, which also hosts a lava lake. Eruptions of lava have continued intermittently in the East Rift Zone ever since.
Is this how it erupts normally?
The short answer is yes, but the long answer is worth exploring. The broad, rounded shape of the Hawaiian islands and the nature of their eruptions are due to basaltic magma. Basaltic magma has a low viscosity, which prevents it from piling up like the thicker magmas responsible for angrier, pointy volcanoes like Mt. St. Helens. Instead of erupting explosively and filling the sky with ash, Hawaiian volcanoes tend to simply barf up lava flows—which can generally be escaped at a brisk walking pace.
Kīlauea’s main magma chamber seems to be a few kilometers below Halemaʻumaʻu Crater at its summit. When the volcano’s guts gurgle with a new injection of magma from below, the lava lake in Halemaʻumaʻu Crater rises. The conduits and crevices that constitute Kīlauea’s “plumbing” extend from the summit region over to the East Rift Zone. So after lava rises in Halemaʻumaʻu Crater, the lake sometimes drains back down as the new magma moves on toward the eastern section of the volcano.
Just a few years ago, the town of Pāhoa—just a couple miles from the current eruptions—was in the news as a lava flow creeped in its direction. That eruption, which started near Pu‘u ‘Ō‘ō Crater, involved lava pouring relatively quietly out of cracks called “fissures” that opened in the ground. This is a common fate for magma piped into the East Rift Zone. The lava from these fissures can sometimes fountain high into the air, driven by pressurized gases that also escape through the fissures, but there is no plume of ash.
Hawaii is occasionally capable of more violent eruptions, though. Cinder cones are piles of rubble you might recognize as porous “lava rock” used for landscaping. They are created by frothier versions of fissure flows, with higher gas content that causes material to sputter higher (and more dangerously) into the air.
More rarely, lava lakes like Halemaʻumaʻu can trigger explosive events when they drain. Normally, the magma beneath the lake maintains a sort of demilitarized zone with the surrounding groundwater—a vapor buffer that separates the two. But if the lava lake level falls below the water table, the uppermost groundwater can seep into the open tube and drop down into the magma, flashing to steam. Because the exposed walls of the lava lake crumble without the lava there, a collection of blocks can clog up the neck of the tube. That can allow the pressure of the steam to build until it blasts through.
That’s exactly what happened in 1924, launching huge boulders like cannonballs and producing a fair amount of ash. The lava lake in Halemaʻumaʻu Crater disappeared afterward until one opened up again in 2008.
What happened now? Were there any warning signs?
Almost four weeks ago, it became clear something could be brewing. The number of small earthquakes within the volcano—produced by the movement of magma—ramped up. And as the lava lake at Halemaʻumaʻu began rising, precise satellite and ground sensor measurements showed that Kīlauea was inflating—clear signs that some fresh magma had been delivered. Eruptions don’t always follow volcano inflation, but it’s a darn good sign that the risk has increased.
#Sentinel1 #InSAR outcome for Apr 19-Would possibly 1 (6 pm native) from #Kilauea displays deformation because of ongoing magmatic intrusion. Magma withdrawn from heart East Rift Zone and intruded underneath decrease East Rift Zone. No coincident deflation of summit. Replace: https://t.co/sfajMPjR8Z pic.twitter.com/szjuyk2b5D
— USGS Volcanoes🌋 (@USGSVolcanoes) May 2, 2018
Subsequent, the summit lava lake degree fell greater than 30 meters on Would possibly three, Pu‘u ‘Ō‘ō Crater’s lava lake additionally gave the look to be as much as one thing, and the primary lava fissures spread out in Leilani Estates. Whilst the East Rift Zone persevered inflating, the summit of Kīlauea started to deflate. A helicopter flight round Pu‘u ‘Ō‘ō tomorrow discovered… no lava lake to be seen.
On Would possibly five, Hawaii skilled its most powerful earthquake since 1975—a magnitude 6.nine. The earthquake came about simply offshore and most effective about five kilometers under the skin. This was once an important motion on a fault within the rock slightly than some minor volcanic indigestion, but it surely was once nonetheless associated with the motion of magma throughout the advanced plumbing underneath the volcano. The shaking led to through this and different better earthquakes knocked some rock into the lava lakes, kicking up momentarily horrifying clouds of ash.
In the meantime, extra fissures had been opening up in Leilani Estates. Maximum didn’t produce sufficient lava to achieve a long way from the fissure itself, even though a pair produced significant flows. The better danger was once in fact the volcanic gasoline audibly gushing out of each and every one, polluting the native air. That’s to not diminish the affect of the lavas, in fact—greater than two dozen houses had been destroyed, and the 1,700 evacuated citizens have had restricted alternatives to rescue possessions.
SInce the eruption of the #Kilauea #volcano, sulfur dioxide has spiked at the Large Island. SO2 is a poisonous gasoline that happens naturally in magma. https://t.co/zFNi0j3Dw5 pic.twitter.com/Sa0cbcsGG3
— NASA Earth (@NASAEarth) May 8, 2018
What occurs subsequent?
The fissure eruptions have quieted within the remaining couple of days, however the rumblings underneath the skin point out there’s no reason why to suppose they’re performed. Eruptions may just resume from the prevailing 15 fissures or from new ones that open up alongside the road of the East Rift Zone. At this level, it’s unimaginable to mention how for much longer this is able to proceed.
However since the lava lake at Halemaʻumaʻu has continued falling this whole time—a complete drop of round 300 meters—worry a few repeat of the explosive 1924 eruption is now expanding. If the lava lake falls a lot farther, it’ll achieve the water desk, doubtlessly putting in place a steam blast state of affairs with little or no caution. In consequence, Hawaii Volcanoes Nationwide Park has been closed to stay other folks out of achieve of projectile boulders.
For those who’d love to practice the newest information on those eruptions, widespread updates are to be had from the USGS Hawaii Volcano Observatory and a unique match web page.