Volcano Mt. St. Helens--fiery laboratory. (1981)

[Music] research scientists create products which enrich the quality of our lives products to increase our food supply dyes and pigments which surround us with color suitables to improve our health products which reaffirm the value of science to mankind as part of its continuing program in support of science education siba geige is pleased to present this issue of the science screen report [Music] the science screen report developments in science engineering and medicine that help solve the problems of modern life planet earth has about 600 active volcanoes shield volcanoes like hawaii's mauna loa exude rivers of molten rock or lava forming huge flat shield formations like this one [Music] while strata volcanoes like north america's mount saint helens build up cones of rock and debris explode them away and build them up again [Music] on may 18 1980 mount saint helens erupted with an explosive force of more than 10 megatons of tnt leading to much new knowledge of archaeology chemistry physics and environmental effects this is a report on those discoveries [Music] volcano mount saint helens a display of natural forces which remains a major focus of scientific activity what causes volcanoes to form the theory of continental drift proposes an ancient land mass broke up over millennia resulting in today's continents which continue to drift continents and ocean floors rest on massive basaltic rock plates carried on the dense hot slowly flowing mantle layer below if one continental plate slides under another or is subducted the deeper plate margin melts forming zones of liquid rock magma chambers which may emit liquid rock to the surface this lava forms volcanoes in other cases two plates may drive against each other forming mountain ranges or slip past each other laterally causing huge faults and earthquakes as with california's san andreas fault in still other cases plates move apart allowing sub-crustal material to boil up as in mid-ocean ridges much of the earth's present geology and geophysics can be explained as the result of different plate interactions in particular many plate boundaries delineate belts of volcanoes and earthquakes phenomena we are just beginning to understand in the case of north america's pacific northwest the small gorda plate is subducting the north american plate several centimeters a year setting the stage for major volcanic activity some 30 000 years ago this subductance created a chain of volcanoes including mount rainier lassen baker hood shasta and mount saint helens all having erupted in the past two centuries of these mount saint helens is the youngest and most active and has erupted at least every 200 years for the past 40 centuries a 1978 eruptions hazard study was accurate in predicting the scale of the 1980 eruptive event [Music] during march and april a volcanic hazards team recorded minor earthquakes steam eruptions and a deformation bulge on which sensors were placed as one consequence authorities closed off the surrounding area saving the lives of thousands for at 8 32 am on may 18th mount saint helens erupted it would be more than a year however before the sequence of events leading up to the colossal explosion was revealed infrared weather satellite images detailed the drifting ash clouds eastward movement over the next 30 hours brisk upper level winds swept debris over the central states in two or three days as revealed by these national earth satellite service images such eruptions have long been thought to affect climate by placing volcanic materials into the stratosphere mount saint helens provided data to better evaluate this theory [Music] a pre-eruption color-coded satellite image of mount st helen shows a white snow clad peak treeless slopes in green surrounding forests in red and spirit lake and other bodies of water in black [Music] a post-eruption image of the volcano's aftermath shows debris color-coded in green spreading north from the volcano's collapsed flank spirit lake covered by floating rubble is color-coded brown [Music] a year later the only change is newly sprouted vegetation color-coded yellow the volcanic crater is four kilometers long and two kilometers wide after the eruption bad weather and heavy ash fallout prevent investigation of affected areas but geological survey and sandia laboratory airborne surveys soon follow nearly 600 square kilometers of timber highways recreational areas and homes are found destroyed at the site of a logging operation the powerful lateral blast ripped away this bulldozer's cab roof [Music] and twisted a 33 meter logging crane a glacier fragment lies nearby carried kilometers from the volcano's north side among those lost in the eruption two were scientific observers robert landsberg buried in his car david johnson body not recovered melting ice and snow combined with fine ash and volcanic pumice rocks holding many air bubbles to produce mud flows although light and weight the mud flows were able to carry huge boulders great distances the scientists found that the massive sideways blast had moved at hundreds of kilometers an hour a slower moving debris avalanche composed of huge hot mudflows had climbed over a five kilometer tall mountain range then moved along the tuttle river [Music] displaced lake and river water mixed with ash dirt and melted glacier ice formed more mudflows which raced down the river to destroy roads bridges homes and other artifacts [Music] spirit lake now holds islands of debris loaded with sulfur and metals cooked by heat its ecosystem has shifted large life forms are gone unable to live in deoxygenated water but species of bacteria chemosynthesize energy from metallic compounds and thrive nearby a river valley holds a 200 meter high mass of mud ice debris water and pumice when river water touches hot sediments in the debris the water flashes to steam 20 kilometers or more from the crater scorched trees remain standing between 10 and 20 kilometers away trees were toppled and bark blasted off and closer than 10 kilometers everything was blown away trees grass even topsoil creating a lifeless moonscape despite the chance of new eruptions various scientific investigation teams quickly move in to probe volcanic mysteries blast deposited material is analyzed seeking clues to aid in forecasting future eruptions cars close to the blast are studied and their melted accessories headlights taillights and others collected the melting effects are then duplicated using new ones revealing eruption temperatures reached up to 350 degrees celsius studies of the timber blowdown suggest a blast cloud 10 times as dense as air moving at 100 meters per second seismograph and other measurements along with film taken by those present reconstruct the stages of the eruption last active in the 1850s mount saint helens is formed from the materials of previous eruptions old ash dust hardened lava events in early 1980 minor quake steam eruptions the 300 meter rock bulge rising 2 meters per day suggest growing internal pressure by magma and volatile gases against the overlying rock on may 18th at 8 32 a strong earthquake occurs pressure from within causes the north face to disintegrate and a debris landslide descends into the tuttle river valley uncapping the volcano hot magma and gases breach the north slope moving outwards and downwards reaching the total river the resulting blast wave moving with hurricane force is a massive emulsion of dust ash water ice rock and volcanic materials the eruption continues for over 11 hours mount saint helen's topography has undergone significant alterations still active it continues to serve as an extraordinary natural laboratory [Music] better volcanic eruption prediction techniques are one goal of current research perhaps new systems using data from outgassing crater cracks laser measurements and space satellites eruptions can now be predicted weeks in advance instead of by only minutes or vague centuries the causes of eruptions are also sought as well as insights into quake processes resources distribution and better magma and geothermal power plants [Music] in the past five centuries volcanoes have killed about 200 000 people and destroyed much property in the coming years mount saint helens will be a natural laboratory for scientists studying the world's mountains of fire [Music] science screen report has been produced by siba geiger corporation with headquarters in hardly new york as part of its continuing program in support of science education [Music]