This animation illustrates the breakup of Africa and South America, featuring the eruption of volcanic islands along hot spot tracks in the South Atlantic. Geographic area of interest: South Atlantic Ocean. Geological Time Interval: 200 Ma (early Jurassic) to Modern.
keywords: Pangea, plate tectonics, continental breakup, eustasy, rifting, Central Atlantic, South Atlantic, Indian Ocean, Africa, South America, Madagascar, India, Antarctica, sea floor spreading, hot spots, hot spot tracks, Mid-Atlantic Ridge, mid-ocean ridge, Scotese, animation
Please cite as:
Scotese, C.R., & van der Pluijm, B., 2020. Deconstructing Tectonics: Ten Animated Explorations, "Hot Spots and Hot Spot Tracks", Earth and Space Science,
7, e2019EA000989. doi. org/10.1029/2019EA000989
More Info:
Anomalously hot mantle can create continental and oceanic regions at the surface that are characterized by extensive volcanic activity. These volcanic regions are thought to be due to hot, buoyant, rising plumes of mantle, called mantle plumes, and the associated volcanic activity is called hotspot volcanism (Morgan, 1971). Hotspots are characterized by the deposition of a large volume of volcanic rocks with geochemical signatures that are distinct from subduction-related and ocean ridge
or rift-related volcanism (Sleep, 1992). Especially voluminous hotspots produce oceanic island chains and plateaus.
One modern example of hotspot volcanism is the Hawaiian volcanic island chain in the Pacific Ocean. The mantle is more stationary than the overlying lithospheric plate (moving faster by at least one order of magnitude), so the location of active volcanism changes as the plate moves over the mantle plume with time. This creates a trail of volcanic islands that become older as they move away from the active hotspot (Wilson, 1963). Today, Hawaii’s Big Island is the active part of one such hot spot track, while a series of extinct volcanic islands and submarine volcanoes extend off to the northwest and north, forming the Hawaiian-Emperor island chain.
Some mantle plumes are long-lived, lasting 100 million years or more, while others are short-lived, lasting less than 10 million years. The orientation of a hotspot track provides the direction of plate motion relative to a mantle reference frame, so absolute motion, and the age of volcanic rocks along the track records the velocity of overlying plates.
The opening of the Atlantic Ocean along the Mid-Atlantic Ridge was accompanied by several mantle plumes under the late Paleozoic supercontinent Pangea, including Iceland in the North Atlantic and Tristan da Cunha in the South Atlantic. The South Atlantic preserves a trail of progressively older hotspot volcanism from the southern Mid-Atlantic Ridge, marked today by Tristan da Cunha, to northern Namibia in Africa and southern Brazil in South America.
Closing the Atlantic Ocean shows these two continental areas coming together at ~140 Ma and marks the location of a mantle plume under Pangea at the start of ocean spreading. The Tristan da Cunha hotspot track is especially pronounced in the eastern South Atlantic and is mirrored by a track to the west of the mid-Atlantic Ridge. Notice also that the mirror-image tracks are not parallel to the ridge’s spreading direction, showing that the ridge and plates were together moving in a northerly direction relative to the hotspot (absolute) framework.
8 сен 2024
