DOWNLOAD PDF SEISMIC HAZARDS AT KILAUEA AND MAUNA LOA VOLCANOES, HAWAII

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1 Chapter 1 : How big are the Hawaiian volcanoes? Frequent and long-lasting eruptions and recurrent strong earthquakes in Hawai'i create a unique combination of natural hazards for people across the Hawaiian Islands. This is especially true for residents on the Island of Hawai'i, which consists of five volcanoes, four of which are classified as activeâ KÄ«lauea, Mauna Loa, HualÄ lai. Closer views of the fuming spots within the collapsed area are shown in the two photos posted below. A section of Crater Rim Drive preserved on a down-dropped block is visible at the far right. Even with low emissions, enough gas reaches the surface to produce yellow deposits of native sulfur on the crater walls, as seen here. Since, more than 30 magnitude The Great Hawaii ShakeOut is an annual earthquake awareness and preparedness event held on the third Thursday of October. For more info on earthquake safety, please visit https: Thermal images see inset lower left show no signs of lava within the cone - the small collapse pit in the center of the crater floor is cold. The bottom of the crater appears to still be covered in collapse rubble - there were no signs of any hot material. A large black sand beach remains at Pohoiki. The sand continues to block access to the boat ramp, which is just to the right of the center of the photo. The thick fissure 8 lava flows can be seen in the lower left portion of the image. September 28, Before and after satellite images of Leilani Estates subdivision This comparison shows satellite images of Leilani Estates subdivision before and after. The image on the right, collected in early September, shows that the eastern portion of the subdivision has been covered by lava. The fissure 8 lava channel runs northeast from the fissure 8 cone at the start of the channel. Note also the brown areas of dead vegetation south of the lava flow. Highway runs north-south along the left side of the images. Before and after satellite images of the Fissure 8 area in Leilani Estates A close up comparison of the fissure 8 area in Leilani Estates subdivision. Leilani Avenue runs right-left east-west through the center of the images. On the right side, the crater within the fissure 8 cone is visible. The fissure 8 lava channel extends north from the cone. Pohoiki Road runs left to right through the center of the image. The Puna Geothermal Ventures site is in the upper left portion of the image. Kapoho Crater is in the left portion of the image. Lava filled much of the crater, including the small nested crater that contained Green Lake. The Kapoho Beach Lots subdivision is in the right side of the image, north of Kapoho Bay, and was completely covered by the fissure 8 lava flow. Kapoho Farm Lots, near the center of the image, is also beneath the flow. Since August 4,, the number of earthquakes at the summit have decreased and the rate of subsidence has stabilized. The largest, shown in this webcam image, occurred at about The collapses generated small tilt offsets and seismic energy recorded by nearby geophysical instruments, but had no discernible effect on other parts of the rift zone. On September 4, lava erupted on the crater floor within the vent, building a small cone on the floor and creating a flow that did not extend beyond the vent walls. On September 5, gas bursts briefly lifted the crust over a small opening on the lava flow surface. On September 6, minor incandescence was visible overnight, but only fuming was observed during daylight hours. On September 7, activity was limited to fuming and slight deflation of the lava flow surface near the center of fissure 8. Lava within the fissure 8 crater looked much the same as yesterday, except that the new cone appeared less prominent. Steam in background is due to recent rainfall. The cone formed as lava erupted from an opening on the surface of the flow that covers the crater floor. A closer view of the small cone forming on the floor of crater within fissure 8 today Sept. By this morning, bits of molten lava emitted from the cone every few seconds had built it up to an estimated height of around m about ft. Lava has filled the small footprint-shaped crater inside the cone. Other lower East Rift Zone vents were steaming due to morning rainfall. Page 1

2 Chapter 2 : USGS: Volcano Hazards Program HVO Mauna Loa Background: Mauna Loa is the largest active volcano on Earth. Eruptions typically start at the summit and, within minutes to months of eruption onset, about half of the eruptions migrate into either the Northeast or Southwest Rift Zones. Lecture Notes Movement of Kilauea and Mauna Loa While there is no real consensus on why Hawaiian volcanoes move, the fact is that they do move. One of two things can happen when you apply enough force to move a volcano; neither is particulary good. The Hilina Slump First, the volcano can move or slide fairly easily along its base. Generally the movement is relatively continuous, however a bit of sticking here and there can generate some rather large earthquakes. The structure that results from this type of movement is called a slump. Generally, a large block of the volcano slides coherently and stretches the volcano. Because the block is lengthening, it must also get thinner. The result of this is a set of cuspate normal faults near the head of the slump. The blocks on the seaward side of the fault drop downward due to the fact that the moving block is thinner. The Hilina slide on the southern side of Kilauea is an excellent example of a slump. The large "palis" or cliffs on the south side of Kilauea are the tops of the extensive fault system at the head of the Hilina slide. The faults downdrop blocks towards the coast over feet in places. The downdropped coastal side of the fault blocks are probably tilted back towards the rift zone, but have been filled in by numerous lava flows making them slope very gently about 1 degree towards the ocean. This is a lot of movement for such a large object. One possible reason for this is that Kilauea is in the way of Mauna Loa to the south and may be acting as a "door stop". Occasionally Mauna Loa does appear to move to the south, but when it does it has to essentially shove Kilauea as well. This is a lot of ground to break and as you can imagine it results in some pretty large earthquakes. The last time that this appears to have happened was in and the result was the M8 Kau Earthquake. During this event the entire coastline from Kau to Kalapana was rocked by large earthquakes and probably moved seaward. Another large earthquake struck Kalapana in This time only the south flank of Kilauea moved, but the result was a magnitude 7. Seismic studies show that the seafloor is bent down only a few degrees beneath the south side of Kilauea, making it fairly easy for the volcano to slide. A system of older faults, similar to the Hilina Pali faults, exists on the southeast side of Mauna Loa. These apparently formed before Kilauea became large enough to impede the seaward movement of Mauna Loa. However, the lowest and most northern of these fault systems, the Kaoiki fault, remains very active today. The most recent earthquake along the Kaoiki fault was a M 6. Those nice "Fault Crossing" signs on Highway 11 just past the Park entrance are there to warn you that the Kaoiki fault system sometimes moves the road up and down a few feet kinda hard on the tires if you hit one of these offsets! The southwest quarter of Mauna Loa faces directly out to the ocean like the south side of Kilauea. However, the large palis that are so prominent on Kilauea are absent on this side of Mauna Loa. Instead this side of Mauna Loa is characterized by unusually steep slopes with a pair of arcuate cliffs at either end of this zone Kealakekua Bay at the north end and the Kahuku scarp on the west side of South point at the south end. These two scarps differ from the Hilina pali scarps in that their height increases towards the ocean, while the Hilina scarps generally decrease in size towards the flat coastal plain. Many parts of the submarine flank of Mauna Loa were found to drop off precipitiously into the ocean and the ocean floor at the base of these steep scarps were littered with blocks of rock that are times the size of Kilauea caldera. These deposits were found to distances of more than 50 miles away from the island. If you were standing on the coast and looking out to see, the ends of the deposits would be beyond the horizon. In fact, the scientists studying these deposits could barely see the summit of Mauna Loa from the ship they were using to map the deposits. Dredge samples of the blocks and sampling by deep submersible mini sub a few years later confirmed that these rocks had compositions identical to Mauna Loa and were not old seamounts which would have MORB compositions. The alternative to simple sliding like the south side of Kilauea is complete failure of the flank of the volcano. If the volcano is unable to slide, the pressure builds up Page 2

3 and begins to deform or bulge out the side of the volcano. Eventually the flank of the volcano will fail catastrophically. Such failures result in debris avalanches, which are mixtures of large blocks, pulverized rock, and water. The failure of the north side of Mt. Helens produced a very large debris avalanche deposit. Hawaiian debris avalanches are emplaced below sea level and contain a tremendous amount of water, which makes them very fluid and capable of travelling great distances. Both the forcible intrusion and the deep cumulate model predict that this side of Mauna Loa should be mobile. So are the processes governing Mauna Loa completely different than those controlling the motion of Kilauea or is there some other difference that accounts for this difference in behavior? One of the things to consider is the relative size and position of the two volcanoes. Kilauea is at the end of the Hawaiian Ridge and is fairly small, while Mauna Loa is extremely large and a bit farther into the ridge. We would expect the south flank of Kilauea to sit on seafloor that is just beginning to be bent under the volcano, while the seafloor beneath Mauna Loa should have been depressed much farther and presumably at a steeper angle. In fact, seismic refraction studies show that the ocean crust is bent down at least 10 degrees beneath the west side of Mauna Loa. The size of the debris avalanches and the amount of the material removed caused Pete Lipman to completely rethink a lot of the evolution of Mauna Loa. It now appears that somewhere around, to, years ago a series of massive failures took place on the southwest side of Mauna Loa. These debris avalanches took a huge "bite" out of Mauna Loa, with the two ends of the scar at Kealakekua Bay and South Point. The rough size of this scar is shown by the blue line of the main figure. The headwall scar of these avalanches actually appears to have partially intersected the active rift zone of Mauna Loa! This probably produced some really interesting eruptions, but all of the evidence for whatever might have happened is now deeply buried under the younger lavas. This 3-d drawing by Rick Hazlett gives you a good idea for the size of the piece of Mauna Loa that was removed by the debris avalanche events. The scar created a very low area along the rift that was the easiest place for lava to erupt for a long time. This "low pressure" region appears to have caused the rift to shift westward several miles as it rebuilt in the scar the rift zone is represented by the dikes--the vertical lines--shown on the Lipman diagram. An interesting effect of this was to essentially stop eruptions from reaching the southeast side of Mauna Loa for tens of thousands of years. Erosion was able to begin cutting into the large palis on the SE side of Mauna Loa. Valleys are cut when waterfalls plunge over the cliffs and begin to erode back up slope. Notice that the northern end of this fault system did not suffer the same fate as the Ninole Hills. This is because lava flows from the summit region of Mauna Loa were able to continue covering this part of the fault system. During this time interval, Kilauea also grew up and is banked against Mauna Loa and has grown nearly as high as the tops of this fault system. This map shows the landslides on both Kilauea and Mauna Loa. This map from Moore and Chadwick shows the subaerial and submarine geology on both Kilauea and Mauna Loa. Examination Questions Describe and explain the mechanics of the Hilina slump. Why does it behave in this manner? Describe and explain the landslides on the west side of Mauna Loa. Why do they behave the way they do? Are there any surface expressions of this event today? Extra Reading Moore, J. Rates of lava accumulation vs. If you have comments or suggestions, me at kenhon hawaii. Page 3

4 Chapter 3 : Mauna Loa - Wikipedia Description 97 p.:chiefly ill., maps ;28 cm. Part or all of this report is presented in Portable Document Format (PDF). For best results viewing and printing PDF documents, it is recommended that you download the documents to your computer and open them with Adobe Reader. PDF documents opened from. The extent of the eruption and lava flow has been superimposed on the map shown in red. Had the Mauna Loa inundation maps been available in, they could have been used to determine that the northern portion of Hilo was the most likely area to be impacted by the main lava flow. In this photo, captured from near the Hilo airport, the flow front appears closer to the city than it actually was. Should a similar eruption occur in the future, the U. To this end, HVO scientists assess volcano hazards and inform the public and civic officials using media outlets, community forums, and other outreach activities. When it does, many people, including emergency responders, will need to know which areas are threatened with lava inundation. Researchers at HVO have produced maps that will help Hawaii County Civil Defense and other emergency managers identify people, property, and facilities at risk during future eruptions. A few vents, however, occur along radial fissures that extend primarily north and west from the summit. The bounding walls of Mokuaweoweo create topographic barriers that should protect areas southeast and west of the caldera from lava flows erupted from within the caldera. But the barrier on the west side is rendered ineffective by the radial vents on the flanks of the volcano. For example, in, an eruption from radial vents on the northwest flank of Mauna Loa produced lava flows that advanced to the ocean in eight days. Using detailed geologic mapping and modeling of how a fluid in this case, lava responds to surface topography, USGS-HVO constructed nine maps depicting 18 inundation zones on Mauna Loa. Each zone identifies a segment of the volcano that could erupt lava and send flows downslope. The inundation maps provide a good first-order understanding of specific areas that could be affected by Mauna Loa lava flows once a vent is identified. This information is critical for response planning. When a Mauna Loa eruption starts, the maps can help decision makers quickly identify communities, infrastructure, and roads between possible vent locations and the coast, facilitating more efficient and effective allocation of response resources. The public can also use the maps to consider where lava flows might go once an eruption starts. Geological Survey as Scientific Investigations Map, comprises 10 sheets maps and an explanatory pamphlet. These nine sheets depict the 18 inundation zones for Mauna Loa. Guidelines on how to interpret the maps are provided in the accompanying pamphlet. The inundation zones identified on the maps are: The boundaries between inundation zones are approximate. The names given for each sheet are descriptive, and are meant to represent the larger geographic areas of potential lava inundation. Map scales vary from 1: HVO also plans to distribute paper copies of the maps to public libraries around the island in the next month or so. On the East Rift Zone, the 61g flow remained active, with lava reaching the Kamokuna delta and surface breakouts downslope of Puu Oo. The 61g flows do not pose an immediate threat to nearby communities. Mauna Loa is not erupting. Small-magnitude earthquakes occurred beneath the summit caldera and upper Southwest Rift Zone, mostly at depths less than 3 miles, with some deeper events at depths of miles. GPS and satellite radar measurements continue to show deformation related to inflation of a magma reservoir beneath the summit caldera and upper Southwest Rift Zone. No significant changes in volcanic gas emissions were measured. Two earthquakes with three or more felt reports occurred on Hawaii Island during the past week. Call for summary updates at Kilauea or Mauna Loa. questions to askhvo usgs. Volcano Watch is a weekly article and activity update written by U. Geological Survey Hawaiian Volcano Observatory scientists. Page 4

5 Chapter 4 : USGS maps identify lava inundation zones for Mauna Loa - West Hawaii Today Note: Citations are based on reference standards. However, formatting rules can vary widely between applications and fields of interest or study. The specific requirements or preferences of your reviewing publisher, classroom teacher, institution or organization should be applied. HVO image from, person for scale. It is pictured above rising 13, ft. Since, Mauna Loa has erupted 39 times; its last eruption was in According to USGS estimates, the volcano has erupted an average of once every 6 years over the past Since it has erupted 33 times producting lavas that have covered over km2. The image at right shows Mauna Loa lava flows since warm colors overlain on a 3-d digital elevation model. The view is looking towards the west, with Hilo qt the bottom center, Kilauea at left, and Kona coast on the north. At 60 miles long and 30 miles wide, it makes up half of the entire island. When one considers that the flanks of Mauna Loa sit on sea floor that is about 16, ft 5, M deep, the "height" of this volcano relative to neighboring land the sea floor is more like 30, ft 9, m! Mauna Loa is the largest active volcano in the world. In fact, using this last measure of its height, it is one of the tallest mountain in the world although many mountains, such as Mt. Everest in the Himalaya mountain range, sit higher relative to sea level. So, directly beneath Mauna Loa, the sea floor on which it sits is depressed by and additional 26, ft m. Thus, if one wanted to say how thick at its center is the lava pile that makes up Mauna Loa, one would need to add its above sea level height, its sea floor to sea level height, and the thickness of its depression in the Pacific sea floor. These total 56, ft 17, m. For more details about estimation of the actual thickness of Mauna Loa volcano, see the write up on "How high is Mauna Loa volcano" at the HVO website. The summit of Mauna Loa began inflating slowly between and after a decade of slight deflation, after experiencing a brief swarm of deep long-period earthquakes. But, inflation was fairly steady in and the first half of following a more intense swarm of several thousand deep earthquakesin late, all of which suggested that the magma reservoir within the volcano was swelling. Then inflation slowed again in, ceased in late, and resumed slowly in late, continuing through mid i. Im late Aug, HVO raised the alter level at Mauna Loa because of long-term increased seismicity rates and inflation of the summit as measured by cross-caldera difference. Earthquakes activity increased in early July and continued through Fall, but then slowed significantly throughout and remained at a level of about 10 a week. Activity peaked in Sept. That earthquake swarm was the greatest number of such earthquales since the beginning of the modern HVO earthquake catalog in the s. HVO scientists continue to monitor the volcano closely. Views of some data that led to the Aug activity status upgrade: The last decade of seismicity and deformation at Mauna Loa. Image redrafted from HVO website Get Mauna Loa activity updates from the HVO website A peaceful Mauna Loa as viewed from the summit of Kilauea volcano in March of Mauna Loa is a "shield volcano", which means it is a gently sloping mountain produced from a large number of generally very fluid lava flows. The volcano is constructed of a rock type known as tholeiitic basalt. Mauna Loa shares the Hawaiian hot spot with its smaller active siblings Kilauea and Loihi seamount. You can view a schematic representation of the geometry of this situation HERE. If you would like to learn more about how the Hawaiian islands formed from a single mantle hotspot, visit the Formation of the Hawaiian Islands web page at this site. The earliest written account of a Mauna Loa eruption, based upon the observations of an elderly guide Keaweehu in the Wilkes exploration party to the summit in, says an eruption took place in In, and an eruption from Mauna Loa caused the largest recorded earthquake in Hawaii, a magnitude 8 by modern standards. The lava flow of is said to be one of the greatest flows ever seen by modern observers. An eye witness account by the Rev. Titus Coan is available at this web site The oldest remnants of subaerial Mauna Loa are to be found in an interesting rock formation known as the "Ninole Volcanic Series". These hills form the so-called "Ninole Shield" which is thought to be either the remnants of a pre-mauna Loa volcano, or uplifted blocks of old Mauna Loa from within the Honuapo-kaoiki fault system. Either way, they are some of the oldest exposed rocks on the southern part of the island. Page 5

6 Chapter 5 : Los Angeles Times - We are currently unavailable in your title = {Seismic Hazards at Kilauea and Mauna LOA Volcanoes, Hawaii}, author = {Klein, Fred W.}, abstractnote = {A significant seismic hazard exists in south Hawaii from large tectonic earthquakes that can reach magnitude 8 and intensity XII. Follow site author kenrubin on Twitter On this page.. Mauna Loa has erupted 33 times since with other less well-dated eruptions going back to and before. Eruptions may consist solely of summit activity or they progress down- flank via rift zone dike propagation in the subsurface to feed flank vents. Dates are provided for the ones that are easy to display at this scale 19 of 33 total historical eruptions. The oldest Mauna Loa eruption in written history is said to have taken place in Testimony was taken from Keaweehu, a Hawaiian guide in the Wilkes party who occupied and mapped the summit from to In, and an eruption from Mauna Loa caused the largest earthquake in Hawaii, registering as a magnitude 8 by modern methods. The lava flow of is said to be one of the greatest flows ever seen by modern observers. Read the full account of the Mauna Loa lava flow entering Hilo at this link. The history is in part based on an account by Titus Coan, whose autobiography is proudly hosted on our HCV website. Hilo was threatened by lava during an eruption that began in May from vents on the northeast rift zone and eventually advanced toward Hilo in, reaching it in August of that year. A few lobes came into town, one reaching just 70 m upslope of Komohana Street and another crossing Komohana Street and stalling near the intersection of Mohouli and Popolo Streets, just 1. The sketch at left is by Joseph Nawahi. It shows the lava flow approaching Hilo on February Color and contrast balance in Photoshop from the original by K. The eruption began with high fountaining and a lava flow in, continued downslope through early By mid year it had stalled six miles from Hilo Bay just above what is now Kaumana City subdivision although the eruption at the vent continued. Michael Rhodes of the Univ. Fissures opened up along the Southwest Rift Zone for a distance of over 12 miles. First, floods of liquid lava poured out of the vents and a cloud of fume rose two miles into the air. That activity lasted about four hours. Then, another set of fissures opened up lower on the rift. While activity on the upper portion of the lower fissures lasted a week, the lower portion remained active for about three weeks. A total of seven large lava flows poured out southward and westward. Three of the western flows even reached the ocean. Although the Mauna Loa flow was quite unlike any other historical Mauna Loa eruption, it was unfortunately not well observed during the eruption. This is partly due to the fact that the volcano was covered in cloud at high elevation and helicopters were not in use; so, most of the information we have comes from what happened on Highway 11 during the eruption. In the months and years following the eruption, the vents and flows have been examined and mapped extensively, however. The eruption occurred along almost the entire length of the SW rift zone from to 13, ft and opened up almost simultaneously like a zipper from an essentially continuous vent system. Consequently, lava flows poured down at numerous places on both the west and east side of the rift. The eruption lasted only two weeks. So, given that the flow volume is 4 to 5 times greater than the eruption which lasted 3 weeks it must have been a spectacular eruption. In places the flows were obviously very fluid and flowing rapidly, since they eroded the bases of prehistoric spatter cones during emplacement. It must have been coming downhill like gangbusters! The lava flow was compositionally very heterogeneous, with the upper part of the rift erupting evolved magmas MgO 7 wt. Compositions became more primitive MgO up to 10 wt. However, the lowest elevation flows were the somewhat more evolved MgO 8 wt. The data are consistent with mixing of a relatively primitive magma with an evolved magma that may have been residing in the rift zone this older magma has compositions very similar to the lava produced by the summit eruption. This account from Rhodes, Journal of Geophysical Research, vol 93, pages Click on the Image to view full size Mauna Loa erupted most recently in Volcanic activity remained in the northeast rift for 21 days. This sequence of events resulted in three flow units shades of red to the left ; the flows are numbered 1, 2 and 3 in the image. Prehistoric Eruptions This account based upon data present by Dr. Lockwood in USGS Page 6

7 Professional Paper Radiocarbon dating of charcoal from beneath lava flows of Mauna Loa has provided the most detailed prehistoric eruptive history of any volcano on Earth. After accounting for contradictory dates and averaging multiple dates on single flows, there are at least "reliable" ages on separate lava flows Lockwood, USGS Professional Paper The distribution of these ages has revealed fundamental variations in the time and place of Mauna Loa eruptive activity, particularly for Holocene time. A cyclic model has been proposed by Lockwood, ibid. This latter eruptive style is marked by summit caldera collapse possibly associated with massive eruptions of picritic lavas low on the rift zones. Concurrent with this increased rift zone activity, the summit caldera is gradually filled by repeated smaller summit eruptions; then, stress across the rift zone increases, magma rises more easily to the summit, rift activity wanes, and the cycle repeats itself. Two such cycles have been recognized within the late Holocene, each lasting 1,, years. However, evidence for earlier such cycles is obscure. Mauna Loa appears to have been quiescent between ka, for unknown reasons. A period of increased eruptive activity marked the period of ka, coincident with the Pleistocene-Holocene boundary. Other volcanoes on the island of Hawaii for which limited radiocarbon data are available show no evidence of similar cyclicity or repose. Page 7

8 Chapter 6 : How long will Kilaueaâ s eruption last? Science News Mauna Loa and Mauna Kea as seen from KÄ«lauea's lower East Rift Zone Low sulfur dioxide gas emissions on KÄ«lauea have resulted in greatly diminished vog (volcanic air pollution) in Hawaii, giving rise to spectacular views on the island. Since then, the volcano has remained active, with a history of effusive and explosive eruptions, including 33 eruptions since the first well-documented eruption in In addition, much of the mountain is invisible even underwater: The shield-stage lavas that built the enormous main mass of the mountain are tholeiitic basalts, like those of Mauna Kea, created through the mixing of primary magma and subducted oceanic crust. There is also a less definite northward rift zone that extends towards the Humuula Saddle marking the intersection of Mauna Loa and Mauna Kea. These models predict a 1. However, analysis of the chemical composition of lavas from the two volcanoes show that they have separate magma chambers, and are thus distinct. Nonetheless, their proximity has led to a historical trend in which high activity at one volcano roughly coincides with low activity at the other. The damage was so extensive that the headwall of the damage likely intersected its southwestern rift zone. Mauna Loa is tall enough to have experienced glaciation during the last ice age, 25, to 15, years ago. It is speculated that extensive phreatomagmatic activity occurred during this time, contributing extensively to ash deposits on the summit. This cyclical behavior is unique to Mauna Loa among the Hawaiian volcanoes. The cause of this cessation in activity is not known, and no known similar hiatus has been found at other Hawaiian volcanoes except for those currently in the post-shield stage. Thus the first entirely confirmed historically witnessed eruption was a January event; since that time Mauna Loa has erupted 32 times. Mauna Loa continued its activity, and of the eruptions that occurred in,,,, twice,,,,, and, [39] three in,, and were partially subaerial. The bombing, conducted on December 27, was declared a success by Thomas A. Jaggar, director of the Hawaiian Volcano Observatory, and lava stopped flowing by January 2, However, the role the bombing played in ending the eruption has since been heavily disputed by volcanologists. Eventually, the eruption ceased on its own. The eruption was not the most voluminous eruption on the volcano the long-lived â event produced more than twice as much material, but it was easily one of the fastest-acting, producing the same amount of lava as the eruption in a tenth of the time. Although there was no loss of life, the village was permanently destroyed. However, the flow got no closer, as two natural levees further up its pathway consequently broke and diverted active flows. Page 8

9 Chapter 7 : USGS addresses rumors: 'Mauna Loa is not erupting' Movement of Kilauea and Mauna Loa: While there is no real consensus on why Hawaiian volcanoes move, the fact is that they do move. One of two things can happen when you apply enough force to move a volcano; neither is particulary good. Red lines depict the rift zones on Mauna Loa left and Kilauea right. With a magnitude estimated at 7. Photo by Henry L. Brigham, Bishop Museum Press, This week marks years since the largest earthquake to strike Hawaii in the last two centuries. Estimated to have been at least magnitude It was felt as far away as Kauai and stopped clocks on Oahu. Stone buildings and walls were destroyed as far away as Hilo. A mudslide in Wood Valley north of Pahala buried 31 Hawaiians. The waves caused damage from South Point Kalae to Cape Kumukahi Kapoho, destroyed more than structures, and took 47 lives. Its size would also rival two of the most deadly events of the past decade: In Hawaii, the most destructive earthquakes occur along a gently sloping fault between the base of the volcanoes and the ancient ocean floor on which they are built. On March 27, an eruption quietly began in Mokuaweoweo, the caldera at the summit of Mauna Loa. Seismic activity increased through the day, and by the afternoon of March 28, a magnitude Earthquakes continued at rates of 50 to per day, including a magnitude A severe aftershock occurred on April 4, and aftershocks of decreasing magnitudes continued for decades. Because of this, Island of Hawaii residents are encouraged to be prepared for both volcanic eruptions and potentially damaging earthquakes. On the East Rift Zone, the 61g lava flow remained active with breakouts on the upper part of the flow field within 1. There were no active lava flows on the pali, coastal plain, or entering the ocean. The 61g flows do not pose an immediate threat to nearby communities. Mauna Loa is not erupting. Rates of deformation and seismicity have not changed significantly over the past week, but persist above long-term background levels. Only a few small-magnitude earthquakes occurred beneath the volcano, primarily at depths shallower than 8 miles. No significant changes in volcanic gas release or fumarole temperature were measured. One earthquake with three or more felt reports occurred in Hawaii this past week. On March 24, at Call for summary updates at Kilauea or Mauna Loa. questions to askhvo usgs. Volcano Watch is a weekly article and activity update written by U. Geological Survey Hawaiian Volcano Observatory scientists and affiliates. Chapter 8 : USGS: Volcano Hazards Program HVO Kilauea Scientists at Hawaii Volcano Observatory closely monitor Mauna Loa, analyzing the seismic activity and changes in the shape of the mountain that might indicate an impending eruption. Chapter 9 : Hawaii Center for Volcanology Mauna Loa Eruptions Mauna Loa, the world's largest volcano, has erupted many times, producing large and long-traveled lava flows, and it will erupt again and pose a significant risk to inhabitants of the Island of Hawai'i. Page 9