The Brink volcano (simply called the volcano in-game) is a location in The Lost Frontier. It is the larger of the two volcanoes on Brink Island, but is the only one visited. It was practically first visited during the mission "Land on Brink Island and search volcano for eco seeker", during which Jak and Phoenix raced to retrieve the eco seeker after it had fallen from the Phantom Blade, fighting off drillbots and armadillos along the way as the lava levels gradually rose.
However, it could have technically first been visited during the mission "Go after Phoenix", wherein Jak pursued Phoenix (each in their Hellcat and Sky Raider, respectively), after the latter nabbed the eco seeker as well as Keira herself. Nevertheless, the coherence of the two places difficult to determine due to ambiguity in the Brink's geography.
The volcano itself is situated north, north-west of Tym's treehouse, which can be accessed via the hangar on the larger island. Beyond the door leading to the volcano is a small cave room with a few cliffs and small lava-falls, requiring the eco construct power to traverse. Ahead of the following door is a small, grassy area with a few cliffs that lead to the inside of the actual volcano, requiring the eco rocket jump power to traverse. Beyond this point the rest of the volcano is explored via successive construct and rocket jump segments allowing Jak to escape four rises in lava levels (which correspond with their own maps).
The volcano primarily consists of rocky cliffs surrounded by lava, with frequent natural dangers such as falling lava boulders, collapsing ground, and vents that release fire from the ground. There were notably some structures that appeared to be either man-made or Precursor-made, such as archways and columns. There were also Precursor statues and Precursor orbs as well, and considering that the rest of the Brink reveals that the environments are largely bolstered by Precursor structures, the volcano could be primarily Precursor-made as well.