Eroded remnants of ancient volcanoes mark today’s landscape in many areas.
The Triassic Period in Earth’s history lasted 50 million years, from 250 million to 200 million years ago. Earth at the time looked vastly different than it does today. All land existed in one supercontinent called Pangaea, which began the Triassic intact but began to break up at the period’s conclusion. Life on Earth went nearly extinct immediately before the Triassic, with more than 90 percent of all species dying en masse. Throughout the Triassic, volcanoes played a major role in shaping land and life, and the remnants and evidences of these landforms exist today.
Northwestern United States
Triassic volcanoes formed the Klamath Mountains and Blue Mountains of Oregon. These volcanoes erupted on top of much older volcanic remnants along Pangaea’s western shore. Igneous rocks from these volcanoes are chemically similar to modern igneous rocks and are rich in iron. These mountains originally grew as underwater volcanoes, and later as island chains as the underwater volcanoes breached the surface. The resulting chain of island volcanoes resembled the Aleutian Islands in scope, although this ancient archipelago rested in warm equatorial waters, surrounded by reefs and atolls.
Occurring 250 million years ago, the volcanic activity in northern Pangaea, now modern-day Siberia, produced the largest discovered basaltic lava fields on Earth’s surface. The area covered in lava equals the square mileage of Alaska. The eruptions expelled effusive lava, which spread like floodwaters over the area for thousands of years. Today, the remaining igneous rock is often miles thick. The estimated timing of the volcanic activity coincides with the largest mass extinction of life on Earth. Paleontologists and other scientists theorize that the eruptions caused the mass extinctions, but other scientists disagree.
Central Atlantic Magmatic Province (CAMP)
Approximately 200 million years ago, large volcanic activity near the center of Pangaea began, beginning the process of splitting the supercontinent into what eventually became the modern world map. This series of eruptions helped create the Atlantic Ocean by driving two halves of Pangaea apart, leaving a narrow but expanding strip of ocean behind. Evidence for these volcanoes is found on both sides of the Atlantic Ocean, in areas like Brazil, West Africa, northwest Spain and the eastern seaboard of the United States.
Along the eastern continental margin of ancient Australia, a mountain range formed approximately 225 million years ago. This event, known as the Hunter-Bowen orogeny, resulted from two tectonic plates colliding. One plate subducted, or passed underneath, the other plate. The top plate was pushed up, and mountains and volcanoes formed along the boundary line between the two plates. Eroded remains of this mountain range exist in northeastern Australia.