STREAMING NOW: Watch Now

Geologist: It's not just lava making the volcano blow

What happens when lava meets water? One might be tempted to think that lava just pours forth, quickly cools down and ...

Posted: May 26, 2018 1:46 PM
Updated: May 26, 2018 1:46 PM

What happens when lava meets water? One might be tempted to think that lava just pours forth, quickly cools down and solidifies. But it is a lot more complicated -- and sometimes more explosive -- than that. Indeed, water plays many roles in volcanology, and the Kilauea eruption that has transfixed us all for weeks showcases them quite clearly.

First of all, water drives "lava fountaining" -- the sustained emission of fluid lava hundreds of feet into the air that has riveted so many people to Kilauea's "lava cam." Magma ("lava" that has not yet surfaced) stored underneath the volcano in its feeding system -- in the Earth's crust -- contains just under 1% of water by weight. As magma rises toward the surface of the Earth, the pressure it is under decreases, making it impossible to keep the water dissolved.

Just think about opening a bottle of soda -- by unscrewing the cap, you release the pressure and all of a sudden lots of bubbles (carbon dioxide in that case) suddenly "appear," or, rather, separate from the liquid and become visible. In volcanology, we say that they "nucleate."

Once they have nucleated, those light, buoyant bubbles rise toward the surface faster and faster. As they do, they keep growing bigger and bigger, expanding as surrounding pressure decreases. As bubbles rise, they drag magma along. By the time they get to the surface, they are moving so fast that they overshoot the crater and head toward the sky, forming a lava fountain.

Lava fountains then feed lava flows. After journeying through Kilauea's East Rift Zone, lava meets water again as the flow enters the ocean. Underwater, lava changes its appearance, forming lava pillows. This "pillow lava" -- spherical blobs of lava that cool from the outside in -- piles up and forms a steep underwater slope called a lava delta. As they are made up of loose blocks of lava amassed chaotically, lava deltas are very unstable and prone to collapse suddenly.

Still at a temperature exceeding 2000 -F, lava turns the surrounding ocean water into a rising plume of white steam, often acidic -- what is referred to as "laze." For the most part, this activity is toxic but nonviolent.

However, water can become trapped among the pillow lava and cause violent explosions at the shore. The process driving them is called Molten Fuel Coolant Interaction (MFCI). It is caused by the sudden contact of a hot molten fuel (lava) and a cold volatile fluid (water).

As the lava enters the ocean, a thin film of steam rapidly develops at the interface between molten lava and liquid water, keeping them separated. This ultra-thin, vapor buffer layer is very unstable, and can collapse in seconds. When it does, lava and water come into contact, triggering a chain reaction of growing intensity that causes a big underwater explosion. Incandescent shards of glassy lava blast in all directions, blanketing the surroundings in translucent, sharp fragments of newly forged Earth.

Meanwhile, up at the summit, water is causing phreatic eruptions inside Halemaumau crater. Phreatic eruptions occur when water flashes to steam. Water from the water table, which sits just over 50m above sea level, gets trapped inside the crater, where it heats to the point of quickly turning to steam, leading to violent explosions in which some of the crater walls turns to ash. In a phreatic eruption, magma doesn't come into play at all.

All eyes are on the lava these days, including my own, but as you watch summit explosions, lava fountains and ocean entries do not forget -- the driving force behind it, in one form or another, is water.

Mississippi Coronavirus Cases

Data is updated nightly.

Confirmed Cases: 96677

Reported Deaths: 2911
CountyConfirmedDeaths
Hinds7143160
DeSoto559460
Harrison388374
Jackson350570
Madison331089
Rankin330679
Lee273670
Forrest248973
Jones248779
Washington225977
Lafayette219139
Lauderdale2059125
Bolivar184566
Oktibbeha179952
Lamar171635
Lowndes158058
Neshoba1579104
Panola149930
Sunflower147146
Leflore141081
Warren140750
Pontotoc127816
Pike124051
Monroe123568
Copiah119133
Scott117627
Coahoma116329
Marshall110617
Lincoln110253
Holmes109859
Grenada109036
Yazoo106230
Simpson104646
Tate100437
Union99824
Leake96038
Adams94137
Wayne90421
Pearl River89253
Marion86535
Prentiss86217
Covington82722
Itawamba82621
Alcorn82011
George78013
Tallahatchie77321
Newton77224
Winston74219
Tishomingo69038
Chickasaw68424
Tippah67117
Attala66725
Walthall60126
Clarke60046
Clay59518
Hancock58722
Jasper57515
Noxubee55116
Smith53415
Calhoun52112
Tunica49715
Claiborne46516
Montgomery46420
Yalobusha43514
Lawrence43313
Perry42419
Greene38817
Humphreys37715
Quitman3775
Stone37412
Jefferson Davis34211
Webster33813
Amite33210
Carroll31912
Wilkinson30518
Kemper29015
Sharkey26613
Jefferson2439
Benton2273
Franklin1933
Choctaw1866
Issaquena1053
Unassigned00

Alabama Coronavirus Cases

Confirmed Cases: 134231

Reported Deaths: 2357
CountyConfirmedDeaths
Jefferson19676351
Mobile13373292
Montgomery8834184
Tuscaloosa8621118
Madison788178
Shelby597849
Lee589760
Baldwin547750
Marshall394343
Calhoun351544
Etowah349045
Morgan329228
Houston290321
Elmore266748
DeKalb241621
St. Clair232235
Walker231684
Talladega216629
Limestone210120
Cullman189920
Dallas179026
Franklin177129
Autauga176425
Russell17603
Lauderdale171333
Colbert164626
Blount161115
Escambia160824
Chilton158530
Jackson157511
Covington140127
Dale138644
Coffee13486
Pike119810
Chambers116442
Tallapoosa116085
Clarke109116
Marion96429
Butler91239
Barbour8827
Winston74412
Marengo72020
Pickens66214
Bibb65410
Lowndes65327
Randolph64713
Hale63528
Geneva6254
Lawrence62023
Cherokee60813
Bullock60414
Monroe5898
Clay5858
Washington55713
Perry5416
Crenshaw53732
Conecuh53511
Wilcox53111
Henry5055
Macon48018
Fayette4578
Sumter43819
Cleburne3805
Lamar3672
Choctaw34712
Greene30315
Coosa1713
Out of AL00
Unassigned00
Tupelo
Clear
72° wxIcon
Hi: 86° Lo: 68°
Feels Like: 72°
Columbus
Clear
73° wxIcon
Hi: 87° Lo: 66°
Feels Like: 73°
Oxford
Clear
66° wxIcon
Hi: 83° Lo: 66°
Feels Like: 66°
Starkville
Clear
66° wxIcon
Hi: 85° Lo: 64°
Feels Like: 66°
WTVA Radar
WTVA Temperatures
WTVA Severe Weather