Geology
The present-day cone of Mount Baker is relatively young; it is perhaps less than 100,000 years old. The volcano sits atop a similar older volcanic cone called Black Buttes, which was active between 500,000 and 300,000 years ago. Much of Mount Baker's earlier geological record eroded away during the last ice age (which culminated 15,000–20,000 years ago), by thick ice sheets that filled the valleys and surrounded the volcano. In the last 14,000 years, the area around the mountain has been largely ice-free, but the mountain itself remains heavily covered with snow and ice.
Isolated ridges of lava and hydrothermally altered rock, especially in the area of Sherman Crater, are exposed between glaciers on the upper flanks of the volcano; the lower flanks are steep and heavily vegetated. Volcanic rocks of Mount Baker and Black Buttes rest on a foundation of non-volcanic rocks.
Deposits recording the last 14,000 years at Mount Baker indicate that Mount Baker has not had highly explosive eruptions like those of other volcanoes in the Cascade Volcanic Arc, such as Mount St. Helens, Mount Meager or Glacier Peak, nor has it erupted frequently. During this period, four episodes of magmatic eruptive activity have been recently recognized.
Magmatic eruptions have produced tephra, pyroclastic flows, and lava flows from summit vents and the Schriebers Meadow cinder cone. The most destructive and most frequent events at Mount Baker have been lahars or debris flows and debris avalanches; many, if not most, of these were not related to magmatic eruptions but may have been induced by magma intrusion, steam eruptions, earthquakes, gravitational instability, or possibly even heavy rainfall.
Read more about this topic: Mount Baker