This small pit crater (100 m diameter) was forested and almost invisible until an eruption in July 1974 sent lava into the shallow crater. Lava partly filled the crater to a depth of 15 m, but about two-thirds of this lava later drained back into a fissure that cut its east crater wall. The high-lava mark is clearly visible on the crater walls.
This view is toward the south from atop the 1974 lava flow.

Lua Mau Crater is generally considered to be the uppermost crater along the Chain of Craters in the upper east rift zone. Technically, however, Lua Manu is within Kilauea's caldera, the outermost boundary of which is a fault between Lua Manu and Puhimau. Moreover, Keanakako`i Crater, generally considered to be within the caldera, is directly along an extension of the Chain of Craters and could be considered part of the upper east rift zone. It is good to remember the old adage that only humans and pigeons make pigeon holes..
Superb examples of lava trees and molds are found in the July 1974 lava flow northwest of Lua Manu Crater. The lava moved through a forest of `ohi`a trees and submerged the lower 3-5 m of the tough, moist trunks. As the peak flow passed through the area, the surface of the flow subsided, leaving the trunks standing above the new ground surface but coated with a rind of solidified lava.
--- http://hvo.wr.usgs.gov/gallery/kilauea/erz/uppererz.html