The northeast face of Mount Abbot is most easily reached from the Mono Pass Trail. Start from Mosquito Flat trailhead, follow the Mono Pass trail south to Ruby Lake, where you can spot Mount Abbot through the gap in the south. West side of the lake are some high granite walls (the "Ruby Walls", class 5 climbing). Contour along the left (East) shore line of the lake, climb up to the gap, which follows the drainage to Mills Lake and a few small tarns. Mount Abbot is always visible in the south.
The Northeast face of Mount Abbot can also be reached from Treasure Lakes. Start from Mosquito Flat trailhead, follow trail toward Morgan Pass for about 4 miles. After passing Long Lake and before descending to Jewel Lakes, ascend the slabs on the right to the top of ridge, then follow it southward until you see Treasure Lakes on the other side of the ridge. Descend the ridge to reach the four lakes.
The NE couloir is the one reaching higher up the mountain than all others, and directly faces the direction of Mills Lake. It is to the left (south) of the notch between Mt. Abbot and Mt. Mills (the notch leads to the Petite Griffon, but NOT to Mt. Abbot's summit).
Follow the NE couloir up, which is close to 40 degrees in the steeper parts. Go right to reach the loose class 3 rocks at a point about 1000 ft from the bottom. In dry years this point is close to the top of the snow, in wet years it is about halfway up the couloir. Climb the rocks diagonally up and right until reaching the summit ridge. Follow the ridge left toward the summit, passing through a narrow knife edge where it is necessary to climb down on the right (west) side, skirt the class 4 rocks on the crest, then climb back over to the east side when possible. Take a few minutes to study the terrain and you should see the more obvious route to keep this easy class 3. After this section scramble up on class 2 rocks to the summit. A part of this is a snow field in early season.
Comments by snwburd
: The NE couloir is the large snowfield to the left (south) of the notch between Mt. Abbot and Mt. Mills (the notch leads to the Petite Grifon, but NOT to Mt. Abbot's summit). Coming from Treasure Lakes, the NE Couloir is less obvious. From the saddle between Mt. Abbot and Treasure Peak, the couloir leading to the Petite Grifon looks to be the correct route. It's not! That one cost me an extra 700 feet of climbing. :)
Climb the NE couloir until you can reach the class 2-3 loose rock on the right side (the left side is dangerous due to the cannonade of rocks that often come down as the temperatures warm). In dry years this is close to the top of the snow, in wet years it is about halfway up the couloir. This loose sand and rock is terrible, but it is the worse part. Look for ducks that lead diagonally up and further to the right. The climbing improves nicely.
At the ridge, head south to the summit. There is an narrow, airy section you must pass before getting to the easy class 1 of the summit massif. The airy bridge is easier than it looks. After crossing the bridge, climb down on the right (west) side, skirt the class 4 rocks on the crest, then climb back over to the east side when possible. Take a few minutes to study the terrain and you should see the more obvious route to keep this easy class 3.
Ice Axe is recommended in all seasons. Ice axe and crampons may be both required if the snow couloir is icy in late summer and fall. A helmet is highly recommended due to rockfall danger.
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