Mount Baker was built from stacks of lava and volcanic breccia prior to the end of the last glacial period, which ended about 15,000 years ago.
Two craters are on the mountain.
Ice-filled Carmelo Crater is under the summit ice dome.
This crater is the source for the last cone-building eruptions
The highest point of Mount Baker, Grant Peak, is on the exposed southeast rim of Carmelo Crater, which is a small pile of andesitic scoria lying on top of a stack of lava flows just below.
Carmelo Crater is deeply dissected on its south side by the younger Sherman Crater.
This crater is south of the summit, and its ice-covered floor is 1,000 ft (300 m) below the summit ice dome.
This crater is the site of all Holocene eruptive activity.
Hundreds of fumaroles vent gases, primarily H
₂O, CO
₂, and H
₂S.
Lava flows from the summit vent erupted between 30,000 and 10,000 years ago, and during the final stages of edifice construction, blocky pyroclastic flows entered the volcano's southeastern drainages.
An eruption from Sherman Crater 6,600 years ago erupted a blanket of ash that extended more than 40 mi (64 km) to the east.
Today, sulfurous gases reach the surface via two fumarole pathways: Dorr Fumarole, northeast of the summit, and Sherman Crater, south of the summit.
Both are sites of hydrothermal alteration, converting lavas to weak, white-to-yellow clays; sulfur is a common mineral around these fumaroles.
At Sherman Crater, collapses of this weakened rock generated lahars in the 1840s.
Mount Baker was built from stacks of lava and volcanic breccia prior to the end of the last glacial period, which ended about 15,000 years ago. Two craters are on the mountain. Ice-filled Carmelo Crater is under the summit ice dome. This crater is the source for the last cone-building eruptions
The highest point of Mount Baker, Grant Peak, is on the exposed southeast rim of Carmelo Crater, which is a small pile of andesitic scoria lying on top of a stack of lava flows just below. Carmelo Crater is deeply dissected on its south side by the younger Sherman Crater. This crater is south of the summit, and its ice-covered floor is 1,000 ft (300 m) below the summit ice dome. This crater is the site of all Holocene eruptive activity. Hundreds of fumaroles vent gases, primarily H
₂O, CO
₂, and H
₂S.
Lava flows from the summit vent erupted between 30,000 and 10,000 years ago, and during the final stages of edifice construction, blocky pyroclastic flows entered the volcano's southeastern drainages. An eruption from Sherman Crater 6,600 years ago erupted a blanket of ash that extended more than 40 mi (64 km) to the east. Today, sulfurous gases reach the surface via two fumarole pathways: Dorr Fumarole, northeast of the summit, and Sherman Crater, south of the summit. Both are sites of hydrothermal alteration, converting lavas to weak, white-to-yellow clays; sulfur is a common mineral around these fumaroles. At Sherman Crater, collapses of this weakened rock generated lahars in the 1840s.
Mount Baker