JUST IN: At least 90 Americans missing after Nepal flash floods

♪ ♪. >> Will: FOX NEWS ALERT, SEARCH-AND-RESCUE TEAMS RACING. AGAINST TIME AFTER A. CATASTROPHIC FLASH FLOOD TORE. THROUGH TOWNS AND VALLEYS ALONG. THE NEPAL CHINA BORDER. AT LEAST THREE PEOPLE ARE DEAD, MORE THAN 1400 PEOPLE ARE STILL. UNACCOUNTED FOR, AT LEAST 90 OF. THEM ARE AMERICANS. YOU MAY HAVE S SEEN IMAGES ON. SOCIAL MEDIA AND THEY ARE. DISTURBING, PEOPLE COVERED HEAD. TO TOE IN MUD BEING CARRIED TO.

SAFETY. ENTIRE HOMES, CARS SWEPT AWAY. BRIDGES, COLLAPSING UNDER THE. FORCE OF WATER. SO HOW DID THIS HAPPEN? LET'S TAKE A LOOK OVER AT THE. WALL. EXPERTS SAY IT WAS TRIGGERED BY. A MASSIVE GLACIER COLLAPSE, IT. STARTED AT AROUND 8:37 A.M. YESTERDAY MORNING, THAT IS WHEN. A MASS OF ICE AND ROCK BROKE. LOOSE NEAR THE NEPAL CHINA. BORDER, CHINA, NEPAL.

THIS ICE AND BOULDERS AND DEBRIS. FELL CREATING A NATURAL DAM AT. THE BASE OF THE RIVER, THAT. NATURAL DAM EVENTUALLY GIVES WAY. AFTER HAVING FOR A PERIOD OF. TIME BUILT UP PRESSURE. THEN SUDDENLY A WALL OF WATER. AND DEBRIS GOES RACING. DOWNSTREAM, TEARING THROUGH. COMMUNITIES IN ITS PATH. IT LEADS TO THE QUESTION AND. LEFT ME WONDERING HOW OFTEN DOES. THIS HAPPEN?

GLACIER FAILURES IN GENERAL ARE. RARE, BUT NOT UNHEARD OF, BETWEEN 19002025 ATLEAST 502. GLACIER FAILURE EVENTS HAVE BEEN. DOCUMENTED WORLDWIDE. 228 DIFFERENT GLACIERS. WE DID SEE ONE JUST IN THE LAST. YEAR, THE GLACIER COLLAPSED IN. SWITZERLAND, ONE PERSON WAS. KILLED IN THAT LANDSLIDE. BUT NOW WITH DOZENS OF AMERICANS. STILL MISSING IN NEPAL THE WHITE. HOUSE HAS FINDING THEM IS THE. TOP PRIORITY. PROFESSOR OF EARTH SCIENCES AT.

THE. UNIVERSITY OF SOUTHERN CALIFORNI. A DOCTOR JOSH WEST JOINS ME NOW. DOCTOR WEST THANKS FOR BEING. HERE WITH US TODAY. SO THE IMAGES ARE BEYOND. DISTURBING, IT IS HARD TO. IMAGINE THE LEVEL OF WATER AND. DAMAGE. HOW SURPRISED ARE YOU BY THIS. NATURAL OCCURRENCE? >> I THINK THIS KIND OF FLOODING. IS SOMETHING THAT UNFORTUNATELY. WE HAVE SEEN SEVERAL TIMES, IN.

OTHER SETTINGS LIKE THIS, YOU. ALREADY MENTIONED THE GLACIER. COLLAPSE IN SWITZERLAND. AND THESE KINDS OF DEVASTATING. EVENTS ARE ONES THAT WE HAVE. SEEN NOW A FEW TIMES. HAVEN'T SEEN ONE THAT HAS CAUSED. AS MUCH DAMAGE AND DESTRUCTION. AND THIS MUCH LOSS OF LIFE. THIS IS REALLY UNSPEAKABLY. TRAGIC, WATCHING THESE IMAGES. AND SEEING THEM AGAIN IS REALLY.

JUST SHOCKING TO SEE. AGAIN THOUGH, THE FACT THAT THIS. HAPPENED IS NOT ON ITS OWN. TREMENDOUSLY SURPRISING. >> Will: WOULD IT BE. INACCURATE TO SAY DOCTOR WEST. THAT IT ALSO WAS A CASCADE OF. EVENTS THAT HAD TO COMBINE. TOGETHER TO MAKE A CATASTROPHIC? IN OTHER WORDS THE GLACIER. FAILING IS ONE THING, THE FACT. THAT THEN IT SORT OF CLOGS UP. FOR A WHILE AND ALLOWS WATER. PRESSURE TO BUILD UP, AND THEN. ALL OF A SUDDEN RELEASES, ALL OF. THIS WATER AT ONCE SEEMS TO BE. THE COMBINATION OF CIRCUMSTANCES.

THAT CREATES THESE HORRIBLE. VIDEOS. >> THAT IS ABSOLUTELY RIGHT, I. THINK ONE OF THE CHALLENGES. THOUGH THAT WE ARE SEEING WITH. THIS KIND OF CASCADE HAPPEN MORE. FREQUENTLY OVER THE PAST SEVERAL. YEARS, IT DOES SEEM LIKE HOW. COULD ALL THESE THINGS CONSPIRE. AT ONCE? INTO THESE STETEEP MOUNTAIN. SETTINGS IT ONLY TAKES A SMALL. LANDSLIDE OR GLACIER COLLAPSE TO. BLOCK A VALLEY AS YOU DESCRIBE, AND FOR WATER TO BUILD UP BEHIND. IT. WE ARE STILL PIECING TOGETHER. EXACTLY HOW THIS PARTICULAR. EVENT HAPPENED, WE HAVE SEEN.

OTHER FLOODS THAT HAVE BEEN. CAUSED FROM THIS KIND OF CASCADE. THAT YOU HAVE DESCRIBED. >> Will: IT JUST MAKES YOU. WONDER IF THE PEOPLE LIVING AT. THE BASE OF THIS VALLEY ALL. ALONG THAT RIVER EVER CONSIDERED. THE POTENTIAL FOR THIS TYPE OF. CONSEQUENCE. I DON'T KNOW THE ANSWER TO THAT, BUT IT IS CERTAINLY HORRRRIBLE O. LOOK AT TODAY. >> ABSOLUTELY. >> Will: I APPRECIATE YOU. BEING WITH.