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Copyright 1985 Lisa Petersen

A Volunteer Project for Hawai`i Volcanoes National Park

First Online Edition, January 1997

The hike to the top of Mauna Loa, the world's largest active volcano, is a long, strenuous, but rewarding walk. This site provides information on things you will need to know before the hike, as well as geology, history and botany of the trail to help make your trip enjoyable and safe.

There are two ways to approach Mauna Loa. The Mauna Loa Trail begins at the end of the Mauna Loa Road on the south side of the mountain in the Park and ends at North Pit where it intersects the Cabin and Summit trails. The Observatory Trail begins at the Mauna Loa Weather Observatory on the north slope of Mauna Loa and ends at North Pit where it intersects the Cabin and Summit trails.

Mauna Loa Mauna Loa Road 6662 ft North Pit 13019 ft 17.0 mi
Obsevatory Mauna Loa Observatory 11040 ft North Pit 13019 ft 3.8 mi
Cabin North Pit 13019 ft Mauna Loa Cabin 13250 ft 2.1 mi
Summit North Pit 13019 ft Mauna Loa Summit +/- 13679 ft 2.5 mi

There are two cabins on Mauna Loa available to hikers: the Pu`u `Ula`ula Rest House, located on the Mauna Loa Trail at 10035 ft, and the Mauna Loa Cabin, located on the east rim of the summit caldera at the end of the Cabin Trail at 13250 ft. Allow two days each way for the Mauna Loa Trail approach, and one day each way for the Observatory approach to the summit cabin.

Most hikers will agree that this is the most difficult hike in Hawai`i. Walking over rough, unstable lava is slow and exhausting. At high elevations, altitude sickness can affect any hiker regardless of his/her physical condition. The weather is usually good, but strong wind, driving rain and snow are possible at any time of year and can make the trip miserable. Some people swear never to hike Mauna Loa again after their first experience, but others make frequent trips for the quiet, solitude and scenery found nowhere else in the world.


If you are staying overnight on Mauna Loa, you are required to register at the Kilauea Visitor Center, where you will receive the latest information about the cabins, water, weather number of people on the trail, etc. Registering for overnight hikes is FOR YOUR SAFETY, and also assists the Park Service in managing the backcountry trail systems.

The cabins on Mauna Loa are available to hikers on a first-come, sharing basis. The Pu`u `Ula`ula Rest House has been recently renovated to accommodate more people than it used to. The Mauna Loa cabin has 12 bunks, foam mattresses, table and chairs. Catchment water in tanks at both cabins should be boiled or purified before use. The chlorine filters at the cabins work surprisingly well to eliminate the chlorine taste. Pit toilets are located next to each cabin. As both cabins are well above treeline, there is no wood for fires or cooking, and FIRES ARE NOT ALLOWED.

Trails on Mauna Loa are marked by ahu (rock piles), and there are signs marking trail intersections, some elevation, and prominent geologic features on the trail. There are no dependable water sources along the trail except at the cabins, so you must carry your drinking water with you. (There are waterholes in cracks along parts of the trail, but the quality of the water is always questionable, and the water is often frozen.)

End of Mauna Loa Road to Pu`u `Ula`ula 7.5 5.0
Pu`u `Ula`ula to Mauna Loa Cabin 11.5 8.1
Mauna Loa Cabin to Pu`u `Ula`ula 11.5 5.1
Pu`u `Ula`ula to Mauna Loa Road 7.5 3.3
Observatory to Mauna Loa Cabin 5.9 6.0
Mauna Loa Cabin to Observatory 5.9 3.1
Observatory to Summit roundtrip 12.6 9.0

These hiking times are averages reported by other hikers and the author's own estimates. Remember that altitude sickness, poor weather, darkness and injury can add hours to these hiking times. START YOUR HIKE AS EARLY AS POSSIBLE.

The climate on Mauna Loa varies from tropic at sea level to sub-arctic at the summit. On the trails, weather is often clear and sunny, but cool. At night, temperatures deop below freezing. Strong wind and driving rain are possible at any time of year. Snow, more common in winter, can be several feet deep and can bury the trail. Snow also reflects sunlight, making snow blindness or severe sunburn likely. The longest day in the summer is about 13.5 hours long; sunrise is as early as 5:40 a.m. and sunset can be as late as 7:05 p.m. In the winter, days are only 11 hours long; sunrise is as late as 7:00 a.m. and sunset is as early as 5:40 p.m. Since twilight is short and it is impossible to follow the trail in the dark, DO NOT GET CAUGHT ON THE TRAIL AFTER SUNSET!

Altitude sickness is common on Mauna Loa, usually above 10000 ft. It can affect anyone regardless of their physical condition, sex, or age, and on one trip but not the next. Symptoms include headache, insomnia, lack of appetite or nausea, dry or wet cough, fatigue, loss of coordination, swollen face or hands, breathlessness, irregular breathing, vomiting and reduced urine output. The only sure prevention is not to go up, and the only cure is to go back down. There are, however, several things that can be done to reduce the possibility or intensity of altitude sickness:

If symptoms persist, give up the hike and return to lower elevations.

Hypothermia, or drop in body temperature due to exposure to the cold and wind, is another hazard to Mauna Loa hikers. To prevent hypothermia, don't get wet. Use rain gear and stay dry. Wear several layers of clothes to keep warm. Synthetic pile or wool clothes are preferable to cotton ones because they will not lose their warmth if they get wet. Wear a hat to prevent heat loss from the head. If you find yourself shivering uncontrollably and you have no more dry clothes to put on, give up the hike and turn back.

There is one more aspect of the Mauna Loa hike that makes the trip difficult: walking on hummocky, unstable, fragile lava is tricky. Locating solid places to put your feet requires full concentration, and it is impossible to develop a comfortable, rhythmic stride. It's a subtle but very real energy drain.

By now you know that hiking on Mauna Loa is nothing close to a casual day hike. BE PREPARED FOR THE WORST! The following is a list of equipment considered essential:

Eruptions of Mauna Loa sometimes occur without warning. If you are on the mountain when an eruption begins, stay away from lava flows and volcanic gasses. Since you are registered at the Kilauea Visitor Center, Park rangers will soon be looking for you.

Wandering off the trail (intentionally or not) can be a fatal journey. It was for one visitor in the winter of 1981. He and his friend set out from the Mauna Loa Road trailhead to see the new snowfall at the higher elevations. They were equipped for a dayhike, wearing shorts, t-shirts, light walking shoes, and carrying no food or water. Somewhere near the 8000 ft level where the trail continues northwest to Pu`u `Ula`ula, the visitor walked off the trail to go straight to the snow. He thought it would be a shorter route, but the friend was reluctant to follow. After a while of rough cross-country walking, the wise friend turned back. The two separated, since the visitor was still determined to reach the snow. The friend walked down some 13 miles through forest before arriving in Volcano Village after dark. A search was begun the next day for the missing hiker. After 7 days for the most extensive air and ground search in the Park's history, no trace of the visitor was found. So if you are thinking about taking a little side trip off the trail, think again.


Mauna Loa is the world's largest volcano. The height of its summit, which fluctuates slightly in response to volcanic pressure, is 13679 ft above sea level, and about 31000 ft above its base on the ocean floor. The volume of Mauna Loa is approximately 10000 cubic miles, or more than 100 times the size of a volcano like Mt. St. Helens.

Mauna Loa is a classic shield volcano with a broad profile like a warrior's shield and gentle slopes averaging 6 degrees. It is a volcano built almost entirely of layers of thin lava flows that spread freely downslope. The lava is basaltic in composition, rich in iron and magnesium and poor in silicon relative to other rock types. Lava flows can be divided into two types based on texture. Pahoehoe lava forms when very hot, gas-rich, fluid lava spreads quickly and cools with a smooth, sometimes ropey, surface. `A`a lava has an uneven, rough, jumbled texture formed by slightly cooler, more viscous lava that crumbles as it flows.

At the top of Mauna Loa is a large crater, or caldera, elliptical in shape, called Moku`aweoweo. This caldera, 2.7 mi long, 1.6 mi wide and up to 600 ft deep, was formed by collapse of the summit. Pressure of magma, or molten rock, in the reservoir below the summit sometimes drops dramatically; the summit area loses its support and portions of it may colllapse. The circular pit craters Lua Poholo, Lua Hohonu and Lua Hou, as well as North Pit and South Pit, were formed in the same way. From the summit caldera, two zones of structual weakness called rift zones extend outward toward the sea. The Mauna Loa Trail follows the upper part of the northeast rift zone, passing many eruptive vents and cones that mark the rift.

Exactly where and how magma is stored within Mauna Loa is still a mystery. During the last few decades, scientists at the U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) have been studying earthquakes and measuring the volcano's response to magma movement (inflation and deflation) in an effort to locate the magma reservoir. Recent studies by the HVO staff indicate a reservoir located 2 to 6 miles below the summit is about the width and length of Moku`aweoweo. Thirty miles below the summit in the earth's mantle layer is a zone of melting, which is the magma source. The magma may rise continuously through fractures in the subsurface rock to the reservoir. An eruption occurs when the pressure forces it to the surface.

In the past 160 years, Mauna Loa has erupted 39 times, or every 3 to 4 years on the average. Most eruptions take place at the summit or on the rift zones, and are very spectacular though gentle and non-explosive. A typical eruption on Mauna Loa begins with the opening of a system of fissures (or cracks) through which lava emerges. Lava fountains from along the fissure, creating a 'curtain of fire.' Within a day or so, the long curtain of fire dies, and the lava becomes concentrated at a single vent. As the eruption continues for days or even months, spatter accumulates around the vent, and lava flows like a river downslope, sometimes reaching the sea and creating new land.

A recent eruption of Mauna Loa broke out on the floor of Moku`aweoweo at about 1:30 a.m. on March 25, 1984. A long curtain of fire formed across the floor of Moku`aweoweo and lasted about 2 hours, coating the caldera floor with pahoehoe a few feet thick. The magma moved underground down the northeast rift zone, broke through the surface, and formed curtains of fire between North Pit and Pohaku Hanalei, and between Dewey Cone and Pukauahi. By late afternoon, the curtains of fire died, and lava poured out of a vent at 9400 ft, located 1 mi below Pu`u `Ula`ula. The eruption continued for 21 days, pumped out up to a million cubic yards of lava per hour (the equivalent to a large houseful every 3 seconds), and sent a lova flow in the direction of Hilo. The flow extended 17 mi before the eruption ended on April 15.


The early Hawaiians walked to the top of Mauna Loa, probably to make offerings to the volcano goddess, Pele. They made a trail up the shortest and steepest flank of the volcano from the old village of Kapapala at 2000 ft to the southeast edge of Moku`aweoweo. The 34 mi hike must have been extremely difficult without shoes, without warm clothes, without backpacks or freeze-dried food. The Hawaiian name of this trail has been lost, but today it is known as the `Ainapo Trail. It is no longer maintained or usable.

The first attempt by a foreigner to climb Mauna Loa was in 1779. John Ledyard, on expedition with Captain Cook, began his assault from the Kona side, but turned back before reaching the summit. Then, in 1794, Archibald Menzies of the Vancouver Expedition succeeded in reaching Moku`aweoweo using the `Ainapo Trail. It took Menzies and his party a week to make the climb.

Charles Wilkes from the U.S. Exploring Expedition climbed Mauna Loa with a party of 300 in late 1840. Fifty of his group camped at Pendulum Peak, 0.6 mi north of the top of the `Ainapo Trail, and spent 28 days on the mountain mapping the summit craters in detail. The remains of Wilkes' base camp can be seen 35 ft south of the present Mauna Loa Cabin.

Not everyone used the `Ainapo Trail to climb Mauna Loa. Some went up from South Kona, others from North Kona via Hualalai. To view eruptions on the northeast rift zone of the volcano, many people walked up from Hilo. And not everyone walked up, either. Sometime around 1870, it became popular to take horses and pack mules up Mauna Loa.

In 1912, the volcanologist and founder of the Hawaiian Volcano Observatory, Thomas Jaggar, suggested that a trail be built along the northeast rift zone to allow convenient access from Kilauea to view Mauna Loa eruptions. In 1915, a segregated company of black soldiers of the U.S. Army constructed the Mauna Loa Trail, which began at the original location of the Hawaiian Volcano Observatory where Volcano House is today, and stretched 30 miles along the rift zone to Moku`aweoweo. It is now possible to drive to the top of Mauna Loa Road past the lower portion on the trail to begin the hike. The original 1915 trail has been rerouted in some places at different times over the years, but the general direction is the same. Today the Mauna Loa Trail is the one most frequently used by hikers.

Also in 1915, the U.S. Army built the Red Hill Rest House at Pu`u `Ula`ula spatter cone. Pu`u `Ula`ula is the oldest spatter cone recognized on the Northeast Rift Zone of Mauna Loa. Flows from the vent have been dated at 8500 y.b.p. (about 6500 years B.C.). Travelers to the summit were forced to bivouac, the favorite place being Jaggar's Cave at the top of the present Observatory Trail. In 1934, a cabin was constructed at North Pit near the 13000-foot sign. The cabin was moved to its present, safer, location in 1940. Many visitors to these cabins over the years have been thankful for the shelter from the cold, wind and snow.

It is also possible to climb Mauna Loa from the north slope, beginning at the Mauna Loa Weather Observatory. The road to the Weather Observatory, constructed by Kulani Prison inmates in 1951, was not available for public use until 1963 when this road was connected to the Saddle Road. Very few people use the Observatory Trail because it is steeper than the Mauna Loa Trail and altitude sickness is more likely because you start at a much higher elevation, making it more difficult to acclimate to altitude. It is also a long drive (1.5 hours or longer from Hilo) to the trailhead, and registration with the Park Service is more difficult.


From the trailhead on the Mauna Loa Road to about 8500 ft, the trail lies in a native forest that is about 2000 years old. Most of the plants are common in other areas of the Hawaiian Islands, while a few varieties are found only at these higher elevations.

The tall trees up to 25 ft at the trailhead are koa (Acacia Koa, pea family), the second most abundant tree in Hawai`i. The sickle-shaped 'leaves' are not really leaves at all, but are flattened leaf stems called phyllodes. True koa leaves, much smaller than the phyllodes, occur on koa seedlings, root sprouts, or injured parts of older trees. Yellow globular-headed flowers give way to flattened, brown seed pods. The wood was highly prized by the early Hawaiians, who used it for canoes, calabashes and surfboards.

The most common endemic tree in Hawai`i is the `ohi`a lehua (Metrosideros polymorpha, myrtle family), which grows from near sea level to treeline at about 8500 ft. The `ohi`a grow up to 15 ft along the trail, and have small, round leaves with usually red blossoms, called lehua, that have long, protruding stamens. The Greek word Metrosideros, meaning heart of iron, is an appropriate name for the `ohi`a. The wood is heavy, hard and dark red. It was used by the Hawaiians to make temple images and the building frameworks. A century ago, `ohi`a was exported for use as railroad ties; the gold spike that connected the transcontinental railroad in 1867 was driven into an `ohi`a tie. Today the wood is used for flooring and paneling.

A less-common tree along the trail is the mamane (Sophora chrysophylla, pea family), identifiable by its yellow flowers. Pinnate leaves are 5 to 6 inches long, and the trees can be 20 to 40 ft tall. The Hawaiians used the durable wood of the mamane for sled runners. Nectar from its flowers is a favorite food of native Hawaiian honeycreepers, and a mamane in bloom is frequently visited by these birds.

Pukiawe (Styphelia tameiameiae, epacris family) is a common shrub easily identified by its small white to purple, berry-like fruits. Leaves are small and oblong, and branches are stiff. The Hawaiians used the fruits in lei. Although the fruits are not poisonous, they are not palatable because of their cotton-like texture.

The `ohelo (Vaccinium reticulatum, heath family) is a small shrub with oblong to circular serrated leaves and yellow to red edible berries sacred to Pele, the volcano goddess. The `ohelo is common in the region between the summit of Kilauea and Pu`u `Ula`ula, and is a very variable species. Another form of `ohelo is seen on Mauna Loa above the 6000-foot level. This plant resembles the other `ohelo, except that the flowers and berries are usually dark purple.

Another common shrub along the trail is the `a`ali`i (Dodonaea viscosa), which grows into trees 20 to 25 ft tall along the Mauna Loa Road. Leaves are spatula-shaped (long and narrow), and pink to marroon winged fruit capsules are conspicuous at branch tips. The Hawaiians used the capsules for dye by boiling them in water, as well as in lei. Hard and durable, the wood was also used for items such as spears.

A member of the geranium family, hinahina (Geranium cuneatum) is a stiff bush with silvery leaves, serrated at the tip, with 5-petaled, white flowers about 0.5 inch in diameter.

Kukaenene (Coprosma ernodeoides, coffee family) is a low trailing shrub with narrow leaves and shiny black berries. The berries are a favorite food of the nene, the native goose, but are not particularly palatable to humans, though used by the Hawaiians as a laxative.

A relative of kukaenene, the pilo (Coprosma montana), occurs long the trail as a shrub with narrow to rounded leaves and orange berries (not tasty). These berries were also used by Hawaiians as a dye.

Smaller plants along the Mauna Loa Trail include native ferns, native sedges, and native and alien grasses.



From Highway 11, turn onto Mauna Loa Road, drive 11.5 miles to the top and park in the small parking lot. LOCK YOUR CAR! If you don't have a car, walk to the road's end or hope for a ride up (traffic is very light). On rare occasions, the Park closes the road because of fire or volcanic hazard; ask at the Visitor Center for the latest information, or call Park Headquarters at (808) 967-7311. Next to the parking lot, you will find a shleter/lookout, pit toilet, trailhead, but NO WATER. Begin your hike here, preferably before noon. Use the detailed guide below to judge your hiking pace by checking off points of interest as you pass them. To convert English measurements to Metric, divide feet by 3.28 to get meters, and multiply miles by 1.62 to get kilometers.

Mauna Loa Trails Map
Summit Area Map

0.0 6662 Sign: "MAUNA LOA TRAIL, RED HILL 7.0, MAUNA LOA CABIN 18.2." Since this sign was put up, the trail has been rerouted and remeasured. The distance to Red Hill (Pu`u `Ula`ula) is now 7.5 mi, and to Mauna Loa Cabin, 19.0 mi. The first part of the trail is level and passes northeastward through native forest growing on old, reddish pahoehoe. Notice how the vegetation cover will decrease dramatically over the next 2 or 3 mi. This is due to the increasing elevation and younger lava flows on the upper slopes. To the southeast is a nice view of Kilauea Volcano on a clear day. Begin in Kipuka Pakekake Quadrangle.
0.3 6717 Trail turns to the northwest, joining the old 1915 trail that began at the Volcano House. Leave Kipuka Pakekake Quadrangle and enter Pu`u `Ula`ula Quadrangle.
0.5 6806 Sign: "MAUNA LOA TRAIL, PLEASE CLOSE GATE." The trail passes through a gate to keep cattle and feral pigs and goats out of the park. CLOSE THE GATE BEHIND YOU! You may see or hear some of these animals over the next few miles. The red pahoehoe you are walking on is about 2000 years old. Filling in some of the low depressions in the lava is volcanic ash, which must be from Kilauea since the ash thins upslope away from Kilauea. To the right (northeast) is a brown `a`a flow about 575 years old, one of several Keamoku flows originating from vents east of Pu`u `Ula`ula.
1.0 7000 Sign: "ELEVATION 7000 FEET, 2134 METERS."
1.9 7400 Behind you is Kulani Cone, a prehistoric cinder and spatter cone covered with vegetation, with 2 antennas on top. It lies on the northeast rift zone. The term 'prehistoric' means before written history, and written history in Hawai`i begins around the time of Captain Cook's discovery of the islands in 1778.
2.5 7900 The trail now turns left (southwest) off the old 1915 trail.
2.7 8000 Sign: "ELEVATION 8000 FEET, 2438 METERS."
3.1 8124 Here the trail joins the trail segment that was built in the 1930's by the CCC.
3.2 8146 BM 1975 R21
3.3 8200 The last `ohi`a tree is seen around this elevation.
4.0 8450 The trail crosses onto prehistoric `a`a (910 years old) with abundant green crystals of olivine. The trail lies on this `a`a and similar pahoehoe for the next 2 mi.
4.1 8514 BM 1975 Q21
4.7 8830 A large trench south of the trail was formed by collapse of the roof of a lava tube. Lava tubes are created when the top surface of a lava river cools and hardens. The lava flowing inside drains out after the eruption is over, leaving a tunnel or tube.
4.9 8920 This is the first opportunity to see Pu`u `Ula`ula to the northwest, still about 2 mi away. To the right of Pu`u `Ula`ula are the 1984 eruptive vents, mostly black in color with a little gold tint to them. Farther to the right (north-northwest) is Pu`u Kulua, a black, flat-topped spatter cone built during late pre-historic time. All these vents lie on the rift zone.
5.2 9000 Sign: "ELEVATION, 9000 FEET, 2743 METERS"
5.3 9010 Above the elevation sign, the trail follows the collapsed lava tube for a while. More than 1 mile to the west are black and silver lava flows of the 1880 eruption. The black flows are `a`a and the silver flows are pahoehoe with a reflective, glassy surface.
6.0 9300 The trail leaves the olive-rich lava at this point. The source of these lavas lies on the rift zone 0.4 mi northeast of Pu`u `Ula`ula.
6.7 9603 BM 1975 P21
7.0 9760 The trail crosses onto red Pu`u `Ula`ula lavas 0.5 mi below Pu`u `Ula`ula. An eruption 8500 years ago created the Pu`u `Ula`ula spatter cone, and the years of weathering has oxidized the iron in the lava giving it its rusty-red color, thus the name 'Pu`u `Ula`ula," meaning red hill.
7.5 10040 Sign: "PU`U `ULA`ULA REST HOUSE, ELEVATION 10035 FEET." The cabin lies on the west side of Pu`u `Ula`ula spater cone. The original 1915 cabin was torn down in 1996 and replaced with a new, larger one. Take some time to explore the top of Pu`u `Ula`ula where you can see much of the island if the weather is clear. A 4-foot-high monument at the top has a plaque with arrows pointing out some of the geographic features. The 1984 Mauna Loa eruption site is located about 2 mi away, in the direction of Hilo. The most prominent cone on the east rift of Kilauea if Pu`u `O`o, site of the 1983-19?? eruption. Around dusk, listen and watch for bats outside. The hoary bat (`ope`ape`a) is one of two land mammals native to Hawai`i. Be sure to PACK OUT YOUR TRASH when you leave the cabin.

0.0 10035 Sign: "MAUNA LOA TRAIL: SUMMIT TRAIL 9.2, MAUNA LOA CABIN 11.3, MAUNA LOA SUMMIT 11.8." Since this sign was put up, the trail was rerouted and the ditances now are 9.5 mi to the Summit Trail, 11.5 mi to the Mauna Loa Cabin, and 12.1 mi to the Mauna Loa Summit. From Pu`u `Ula`ula to North Pit, the trail lies on the northeast rift zone. For the first 1.7 mi, the trail lies partly on prehistoric lavas and partly on 1880 lavas.
0.4 10154 BM 1975 D21. The trail near here lies along the 1880 vents.
0.7 10340 Walk in a lava channel formed during the 1800 eruption. The trail then skirts an unnamed reddish-brown prehistoric spatter cone.
0.9 10419 BM 1975 E21
1.4 10480 The walk proceeds along the red and black spatter cones of the 1800 eruption.
1.6 10689 BM 1975 H21
1.7 10686 The trail starts across a narrow tongue of 1899 `a`a. On the other side of the `a`a, the trail moves onto pahoehoe of 1855 age. The golden frothy surface is formed by gas foaming on the surface of the flow.
1.9 0720 The trail passes along the spatter cones that produced the golden frothy pahoehoe. Look carefully at the spatter fragments for the next 0.1 mi. You might see some small, black, shiny tear-shaped pieces of volcanic glass called Pele's Tears.
2.1 10829 Walk onto 1899 pahoehoe.
2.3 10880 Leave Pu`u `Ula`ula Quadrangle and enter Koko`olau Quad. The 1984 lava buried the trail at this point, and the trail now lies along the north edge of the new flow.
2.5 10960 The trail now moves to the reddish prehistoric spatter of Pukauahi. The name of this cone as it is spelled on topographic maps means smoke hole. The original spelling might have been Pu`u Kauahi, which means the fire hill.
2.6 10970 The trail now crosses onto 1984 lava heading in a southwesterly direction. Be especially careful to stay on the trail here, as the 1984 lava is very shelly (i.e., the surface of the lava is fragile and is often hollow underneath).
2.8 10990 Moving off the 1984 lava, the trail now lies on prehistoric pahoehoe. After a short dog-leg to the right (west), the trail joins the old 1915 trail again.
3.2 11050 To the right (north) are yellow sulphur deposits that mark the 1984 fissures between Pukauahi and a red prehistoric spatter cone just below Dewey Cone.
3.9 11290 The 1915 trail is covered by 1984 lava. Dog-leg to the right, to the Dewey Cone sign.
4.0 11320 Sign: "DEWEY CONE." Dewey Cone was built by the 1899 eruption which broke out here on July 4, 1899, just after the Battle of Manila. The cone was named after Admiral George Dewey who was in command of the U.S. Fleet in that battle. Above the Dewey Cone sign, the old trail was covered by 1984 lava. The new trail follows the north edge of the flow, then crosses the flow for 0.1 mi, and rejoins the old trail.
4.2 11390 The trail lies on red spatter of a fairly old prehistoric cone for the next 0.1 mi, and then drops down several feet to blackish pahoehoe.
4.6 11476 BM 1975 L21. The golden frothy pahoehoe near this benchmark is 1855 lava.
4.8 11550 A trench along the north side of the trail was the main channel of one of the 1855 flows from Steaming Cone, which lies straight ahead.
4.9 11562 The trail drops into the 1855 channel. The cone about 0.5 mi south of the trail is of late prehistoric age. The steaming crack between the prehistoric cone and the trail broke open during the 1984 eruption as magma migrated downrift.
5.0 11580 The trail leaves the golden 1855 pahoehoe and moves onto black and red 1855 `a`a for a short distance, and then descends onto prehistoric greyish tube-fed pahoehoe. The olive-green pumice fragments deposited on the pahoehoe were formed during the eruption of Steaming Cone. The cone 800 feet north of the trail is prehistoric.
5.2 11690 Sign: "STEAMING CONE." Steaming Cone was formed by the 1855 eruption and is one of the main sources of the 1855 lava. The cone emitted steam for some time after the eruption, but in the past 30 or 40 years, steam has rarely been seen. Near the Steaming Cone sign, some of the ahu have cement in them (you may have noticed ahu like this before). These are the remains of a telephone line that once ran from HVO to North Pit in the 1930's. Scientists observing an eruption at the summit could communicate with the Observatory, but the line was more often in need of repair than usable, and was soon abandoned.
5.4 11760 The black `a`a flow south of the trail is 1855 lava.
5.5 11796 BM 1975 M21
5.6 11845 Sign: "WATERHOLE." This waterhole is located in a collapsed lava tube about 100 ft south of the trail. A layer of water overlies ice in the summer; the waterhole is often frozen solid in winter. CAUTION: The quality of this water is questionable! Boil or purify the water before drinking.
6.2 12010 Sign: "ELEVATION, 12000 FEET, 3658 METERS." BM 1926 D1. In the next 0.3 mi, the trail crosses 1975 and 1984 lavas, heading in a southerly direction toward Pohaku Hanalei.
6.6 12210 The trail crosses the 1975 vents and turns to the right (west). Just south of the turning point, there is a black circular spatter rampart. The trail passes along the south side of the 1975 vents for the next 0.1 mi, occasionally crossing onto 1984 lava. The trench to the left of the trail is the main channel from Pohaku Hanalei. It is now filled with 1984 lava.
6.9 12275 Pohaku Hanalei is a prehistoric spatter cone that was cut parallel to the rift by a 1984 fissure. The 1984 lava destroyed the 'Pohaku O Hanalei' sign, buried a bench mark, and covered half of a rock wall windbreak built by hikers. The trail continues along the north edge of Pohaku Hanalei next to 1984 lava.
7.0 12360 Lying on 1984 lava, the trail crosses the rift axis above Pohaku Hanalei in a southwesterly direction, and then turns to the west. Again, be careful not to walk off the trail here. The 1984 lava is very fragile! The trail parallels some vents that were probably formed by the eruption that created Pohaku Hanalei. Near the upper part of these vents, the trail takes off to the southwest across the 1984 flow.
7.4 12530 The large spatter cone about 1000 feet north of the trail is of late prehistoric age.
7.5 12540 At this point, the trail leaves the 1984 lava and moves onto prehistoric pahoehoe.
7.7 12660 Leave Koko`olau Quadrangle and enter Mauna Loa Quad.
7.8 12680 The reddish brown `a`a flow to the right (north) dates from 1935.
8.4 12758 The trail now crosses the 1935 `a`a. Just after dropping off the `a`a flow, the trail is covered by 1984 lava, so bear to the left. The rerouted trail lies on the 1935 `a`a and prehistoric lava for the next 0.7 mi.
9.2 12965 The trail intersects an old abandoned trail that once led to the Mauna Loa Cabin. The trail to the left is not usable. Turn right. After walking 300 feet on this old trail, the new route moves onto the 1984 lava and crosses the 1984 and 1975 fissures.
9.4 13000 Off the 1984 lava, the trail now joins the old trail the rest of the way to North Pit.
9.5 13018 Sign: "ELEVATION 13000 FEET, 3962 METERS." Take a few minutes to look around at the view. North Pit, the crater before you, is covered with 1984 pahoehoe. On the edge of the east caldera wall 2 mi away at the left are 2 large ahu close to the Mauna Loa Cabin. A gap in the wall at the far end of the caldera leads into South Pit. To the right of that are the 1940 and 1949 cones, bisected by the 1984 fissures which are still steaming. On the far side of North Pit (to the west), note how the lava from the 1942 eruption cascaded down the walls. The orignal Mauna Loa Rest House was located just below and to the right. The cabin was built in 1934, but was moved to its present, safer location in 1940 after the 1940 lava came to within 30 feet of the front door. The 1984 lava covered the old cement platform, so the only remnats of the original site are churcks of cement, rusty tin cans, wires, nails, etc. To continue hiking to the cabin, follow the Cabin Trail across the floor of North Pit. The trailheads for the Summit Trail and the Observatory Trail are 0.1 mi to the right. Also to the right, only 375 feet away, is Jaggar's Cave, a shelter from the wind.


0.0 13018 The Cabin Trail begins at the top of the Observatory Trail and heads southwest toward the Mauna Loa Cabin.
0.1 13018 Sign: "CABIN TRAIL, MAUNA LOA CABIN 2.0." It will probably seems longer than 2 mi to the cabin! The trail drops down into North Pit and crosses the crater floor. The trail lies on smooth 1984 pahoehoe, which is probably the nicest walking on the mountain.
0.5 13035 The trail leaves the 1984 pahoehoe and passes very close to Lua Poholo, a pit crater more than 200 feet deep. Lua Poholo was formed by collapse in 1880. Lava from the 1975 and 1984 eruptions spilled info the crater from the north, and lava from the 1880 (?) eruption cascaded down the south wall. CAUTION: The rim of Lua Poholo is severely cracked. For your safety, DO NOT APPROACH TOO CLOSELY!
0.6 13065 The trail now lies on 1880 (?) lava, and begins to climb up to the top of the caldera wall. Take it slowly.
1.0 13165 From here to the cabin, the trail lies on prehistoric flows. Most of these lavas came from overflows of an earlier summit caldera. Be aware that there are a few ahu to the right along the caldera rim that are not trail markers.
1.4 13244 Sign: "TRAIL." On a rise just past this sign you can get a glimpse of the cabin roof, still 0.6 mi away.
2.1 13250 Sign: "MAUNA LOA CABIN, ELEVATION 13250 FEET, 4039 METERS." Congratulations! After resting a while from the long hike, explore around outside the cabin. Just to the south of the cabin are rock walls built by the Wilkes Expedition in December of 1840 (other rock walls are windbreaks built more recently by hikers). Wilkes had 50 men living here in canvas tents for 28 days while mapping the summit region. Farther to the south, a trail about 0.3 mi long leads to a waterhole in a deep crack, more often frozen than not. CAUTION: Boil or purify the water before drinking! The historic `Ainapo Trail ended at this waterhole. The true summit of Mauna Loa is at the opposite side of Moku`aweoweo Caldera. The `a`a on the caldera floor just below the cabin is 1949 lava. Most of the caldera floor is coated with the 1984 pahoehoe averaging 6 feet in thickness. The white boxes and antennas northeast of the cabin are part of the volcano monitoring system on Mauna Loa operated by HVO. Please do not disturb the equipment! The ground around the cabin is littered with light-colored angular rocks blown up by a prehistoric steam explosion within the caldera. After the sun goes down, it will get quite cold. The lowest temperature will be about 10 degrees F. But brave the cold and take a look at the sky. The Milky Way looks like a cloud since the air is so clear, and in June, the Southern Cross can be seen above the southern horizon. Be sure to PACK OUT YOUR TRASH when you leave the cabin.


If you plan to stay overnight at the Mauna Loa Cabin, you must register with the Park Service before beginning your hike. From downtown Hilo, drive up the Saddle Road (Highway 200) 29 miles to Pu`u Huluhulu, turn left, and continue 18 miles to the Mauna Loa Weather Observatory. Allow at least 1.5 hours for the drive. The road has very little traffic, so the chances for hitchhiking up or down are slim. Park in the parking lot for hikers. Take some time to acclimatize and look at the view. Across the saddle is Mauna Kea, an older, more mature volcano than Mauna Loa. Its summit, littered with cinder cones and astronomical observatories, is 13796 feet above sea level. The last eruption on Mauna Kea was probably 3000 to 4000 years ago. At the far left is Hualalai Volcano, which last erupted in 1801 and is still considered active by some geologists. To the northwest, and usually cloud-covered, is the oldest volcano on Hawai`i island, Kohala. Haleakala Volcano on the Island of Maun is visible beyond Kohala. To begin the hike to North Pit, head west along the jeep trail past the parking lot.

0.0 11055 Sign: "OBSERVATORY TRAIL, CABIN/SUMMIT TRAIL JCT 3.5, MAUNA LOA CABIN 5.6, MAUNA LOA SUMMIT 6.0." Add 0.3 mi to these distances to account for the jeep trail length. Begin in Koko`olau Quadrangle.
0.3 11182 Sign: "OBSERVATORY TRAIL, MAUNA LOA CABIN 5.6, MAUNA LOA SUMMIT 6.0." The trail goes up and south from here. Follow ahu and a slightly worn trail on prehistoric lava. This trail was once marked with yellow spots painted on the rocks; you will probably see these spots chipped out of the lava.
0.9 11545 The brown `a`a flow at the left is prehistoric.
1.2 11684 The trail crosses the jeep trail here. This road was built in 1951 to 13450 feet where the first weather observatory was located. After negotiating this miserable road for a few years, the weather observatory was moved to its present location in 1956.
1.3 11768 BM 1978 HVO22.
1.5 11805 A spacious lava tube is marked by two large ahu. Turn around and take a last look at the Weather Observatory. The trail continues to the right following the small ahu (ignore the one at the left).
1.6 11933 BM 1978 HVO21.
1.6 12000 The trail crosses a prehistoric `a`a flow.
1.7 12045 To the left (east) is a prehistoric spatter cone that lies on the north flank of Mauna Loa.
1.8 12072 BM 1978 HVO20.
2.2 12377 Sign: "TRAIL." The old trail continued straight from here, but in 1983, it was rerouted to an easier route. Dog-leg to the left. The rusty brown spots in the grey pahoehoe are weathered olivine crystals.
2.4 12425 Sign: "TRAIL." The trail continues along the jeep trail to the east-southeast. The olivine crystals in the lava here are plentiful.
2.6 12475 Passing another jeep trail to the left.
2.7 12500 Sign: "TRAIL." Just ahead of this point is a locked gate across the road. The jeep trail above here is for use only by HVO and Park Service personnel. The trail turns right (south), following a fissure that produced the flow that the Mauna Loa Observatory lies on.
3.1 12780 The 1942 shiny black pahoehoe flow lies to the right.
3.2 12795 The trail crosses onto the 1942 lava.
3.3 12862 Sign: "TRAIL." Cross the jeep trail straight ahead.
3.5 12970 Leave Koko`olau Quadrangle and enter Mauna Loa Quad.
3.6 12973 The trail crosses the 1942 fissure.
3.7 12989 To the right, placed over a crack, is a primitive toilet.
3.8 13018 Sign to the left: "CABIN TRAIL, MAUNA LOA TRAIL .1, MAUNA LOA CABIN 2.1." Sign to the right: "SUMMIT TRAIL, MAUNA LOA SUMMIT 2.5." Sign behind pointing back down to the Weather Observatory: "OBSERVATORY TRAIL, MAUNA LOA OBSERVATORY 3.5." (The ditance to the Observatory is really 3.8 miles.)


0.0 13018 Sign: "SUMMIT TRAIL, MAUNA LOA SUMMIT 2.5." The trail to the summit begins on 1942 pahoehoe that is mostly black with some golden frothy patches. Only a few feet away from the trail sign is Jaggar's Cave. This is not really a cave, but a section of crack around which hikers have built rock walls for a windbreak. Volcanologist Thomas Jaggar spent many cold nights here while watching eruptions. BM 1926 C1 (13019 feet) is located to the left of the steps that lead into Jaggar's Cave.
0.1 13005 The trail crosses the 1942 fissure, and then continues on prehistoric lavas for the rest of the way to the summit.
0.4 13040 Crack crossing.
0.5 13100 Sign: "SUMMIT TRAIL, MAUNA LOA SUMMIT 2.0." The old Observatory Trail ended here. The trail to the summit continues past the sign in a southwesterly direction.
0.8 13160 There is a faint jeep trail here.
1.5 13390 The trail passes by a HVO seismic station. There is a brick box with a plywood top and an antenna pointed toward the southeast. Please do not disturb the equipment!
1.6 13462 About 0.1 mi to the west is the original location of the Mauna Loa Observatory, built in 1951. Now all that's left is the cement foundation of the little old white building. The HVO has set up a tiltmeter here to measure inflation/deflation of Mauna Loa; the antenna sends the tilt information to HVO by FM signal.
2.1 13656 BM 1926 B1 located off the trail to the west.
2.5 13679 Mauna Loa Summit! BM 1975 A21. The elevation after the 1984 eruption was about 13676 feet as a result of the volcano deflating. Be careful not to get too close to the caldera wall: it is 600 feet down to the bottom!


Note - the Hawaiian language has two markers, the glottal stop (`okina) and the macron (kahako). I have used the back-quote ( ` ) for the glottal stop, but unfortunately it is not possible to put a macron over a vowel in HTML, so all macrons are left out of this online edition.

ahu - heap, pile
`Ainapo - darkened land
Haleakala - house used by the sun
Hualalai - (meaning uncertain)
Kapapala - the Charpentiera shrub
Keamoku - (meaning and spelling uncertain)
Mauna Kea - white mountain
Mauna Loa - long mountain
Moku`aweoweo - red fish section
Kilauea - much spreading
Kohala - (meaning uncertain)
Koko`olau - fluted
Kona - leeward
Kulani - like heaven
Lua Hohonu - deep pit
Lua Hou - new pit
Lua Poholo - pit that sank out of sight
Pohaku Hanalei - (meaning uncertain)
Pukauahi - smoke hole (or maybe original spelling was Pu`u Kauahi, meaning 'the firehill')
Pu`u Huluhulu - fuzzy hill, referring to the vegetation on the cone
Pu`u Kolua - two standing hills (?)
Pu`u `Ula`ula - red hill


Barnard, Walther M., ed., 1990. Mauna Loa - A Source Book vol. 1. 353 pages. Self-published.

Barnard, Walther M., ed., 1991. Mauna Loa - A Source Book vol. 2. 452 pages. Self-published.

Degener, Otto, 1930. Plants of Hawaii National Parks: Illustrative of Plants and Customs of the South Seas. 316 pages. Braun-Brumfield. Reprinted 1975.

Lamoureux, Charles H., 1976. Trailside Plants of Hawai`i's National Parks. 80 pages. Hawai`i Natural History Association. Revised 1992.

Macdonald, Gordon A., Agatin T. Abbott, and Frank L. Peterson, 1983. Volcanoes in the Sea: The Geology of Hawai`i. 517 pages. University of Hawai`i Press.

Macdonald, Gordon A. and Douglas H. Hubbard, 1951. Volcanoes of the National Parks in Hawai`i. 65 pages. Hawai`i Natural History Association. Revised 1989.


Mahalo to Margot Griffiths and Bobby Camara for editing the second edition of the trail guide.

43752 Visitors since 1 Nov 2005.   Thanks for stopping by!
Last updated: April 21 2010 07:36:25.