University:
Arizona State University
Course:
ABS 370 | Ecology
Academic year:

2024
Views:

35

Pages:

2
Author:

Thuyoul US

BASAL TRIASSIC Over the past 250 million years, 11 episodes of massive flood basalt volcanism have occurred worldwide (Figure 143 and Table 9). They are relatively short-lived events, with major phases generally lasting less than 3 million years. This massive eruption created a series of overlapping lava flows, giving many exposures a terrace-like appearance known as traps, from the Dutch word for "staircase." In a brief geological disaster at the end of the Triassic, large rivers of basalt lava flowed out of giant fissures and paved over continental parts of land. A volcanic crisis occurred when all the continents clustered together into one landmass called Pangaea.In a short span of several million years, black basalt erupted along the central spine of the supercontinent, eventually spreading to an area almost the size of Australia. Soon after, the continents split along this axis and separated, thus opening up the Atlantic Ocean.This massive eruption, one of the largest in Earth's history, may have killed most of the planet's life and led to the rise of dinosaurs as rulers of the world. Many flood basalts are located near continental boundaries, where large rifts began to separate the current continent from Pangea near the end of the Triassic. This massive basalt outpouring reflects one of the largest crustal movements in the planet's history. Continents probably traveled much faster than they do today due to stronger plate motion, resulting in tremendous volcanic activity. Triassic basalt common in eastern North America shows the formation of a rift separating the continent from Eurasia.The rift then broke and flooded with seawater, forming the baby North Atlantic Ocean. The Indian Ocean was formed when a rift separated the Indian subcontinent from Gondwana. By the end of the Triassic, India had drifted free and began its journey towards southern Asia. Meanwhile, Gondwana drifted north, leaving Australia still tied to Antarctica behind in the South Pole region. Large basalt flows and granite intrusions occur in Siberia. Extensive lava flows cover South America, Africa, and Antarctica as well. Southern Brazil is paved with three-quarters of a millionth of a square mile of basalt, which is one of the largest lava fields in the world. Major flooding of basalt, 2,000 feet or more thick, covered much of Brazil and Argentina as the South American plate hit the Pacific plate, and subduction fed the magma chamber underlying the active volcano. Basalt flows also blanket areas from Alaska to California. Towards the end of the Triassic, North and South America began to drift away from each other. India, located between Africa and Antarctica, began to separate from Gondwana. The Indochina bloc collided with China. In addition, a major rift began to divide North America from Eurasia.The continental rift radically changed the climate and set the stage for the unusually warm period that followed. After examining early Triassic dinosaurs, the next chapter explores the animals that rose into the air during the Jurassic period.