Field Notes for the Mauna Loa North Slope Field Trip

Transcription

1 Field Notes for the Mauna Loa North Slope Field Trip 22 August, 2012 (Leaders: Darcy Bevens and Jack Lockwood) Checklist of suggested items you should bring: Sun screen Warm clothes (it can be very cold at 11,000 feet, even when sunny) Hat for sun protection & warmth Sunglasses Camera Hiking boots or tennis shoes (the former if you plan to walk over a a flows) Drinking water or Gatorade In the photo below, Darcy and Jack are properly attired in warm clothes. Weather on Mauna Loa ranges from bright sunshine to cold rain and wind. Agenda: We will depart the Waikoloa Hotel at 8:00 in the morning, and drive for 90 minutes to the Mauna Loa Weather Observatory at 11,200 foot elevation. We will then spend the day driving back to our hotel, stopping along the way at points of geologic interest on Mauna Loa s north flank with timing adjusted in order to return to Waikoloa for clean-up and the Conference Dinner at 19:00.

2 Stop 1. We will visit the NOAA Weather Observatory (MLO) and, while we acclimate, learn about the global significance MLO's pioneering monitoring of atmospheric change from an MLO staffer. It is a short hike to view the large USGS-designed lava diversion barrier structure that protects the Observatory from Mauna Loa lava flows. Although MLO is built on 1852 lavas, the barrier designers proudly point out that not a single flow has impacted the Observatory since the diversion barrier was built in 1986! The photo above shows buildings of the NOAA Weather Observatory. Below, looking upslope, a person standing on the barrier provides scale.

3 The oblique air photo below gives an excellent overview of the MLO barriers and shows how it protects the weather observatory complex. Mauna Loa s Northeast Rift Zone is located 4 km away, toward the top of this photo; north is toward the bottom. The western leg of the structure is 670 m in length. Stop 2. Immediately downhill of the Observatory, we will visit and collect samples at an olivine-rich pahoehoe flow that is around 1200 years old.

4 Stop 3. Next up is a visit to a window into a late prehistoric pyroduct, where highly fluid pahoehoe surged out of an opening when the conduit was blocked downstream. Fragments of solid material (pieces of the roof or walls) internally carried in the pahoehoe and now coated by pahoehoe ( lava bon-bons?) now litter the surrounding area. An entrance to the pyroduct is visible at the base of the pit. This stop provides a stunning view of Mauna Kea, including glacial moraines and late-stage cinder cones. Photo above: Bon bons in foreground; Mauna Kea in distance.

5 Stop 4. Lunch will be presented at this beautiful field of pahoehoe, which is much more pleasant to eat on than a a! During lunch hour, explore wellpreserved pahoehoe surface features, including entrail pahoehoe (in the distance), oxidation layers in small tumuli (near hat), or lava worms and lava stalactites in a small pyroduct. Photo above: pahoehoe surfaces. Photo below: Pyroduct wall; GPS for scale, note drips of lava stalactites.

6 Stop 5. A prehistoric a a channel showcases accretionary lava balls; a short walk downhill provides a view of the 1881 pahoehoe overlying a weathered 2,000-year-old flow with ohelo berry bushes - welcome back to denser atmosphere and vegetation!

7 Stop 6. View a collapsed pyroduct, and hike down into it if you wish (our apologies for the trash pile at one end). Stop 7. At Puu Huluhulu, discuss the nature of a pre-holocene Mauna Kea cinder cone and bordering dikes (?), congealed spatter (?), younger lava that sloshed up along the sides of the cone (?), to name a few theories. In addition, see the effect of the surrounding 1935 lava flow on a 19 th -century stone wall.

8 Stop 8. After driving over the high margin of an 1843 a a flow (17 meters), we will visit the plagioclase-rich 1843 lava flow, and if time allows hike out to inspect pahoehoe inflation pits and the largest lava tumuli in Hawaii. Then, we will head back towards Waikoloa, sampling a classic Mauna Kea ankaramite time permitting. MAY THE SUN SHINE, THE FIELD DISCUSSIONS BE MEMORABLE, AND THE FIELD ABRASIONS FEW FOR ALL OF US!