Marie Tharp and Bruce Heezen played crucial roles in advancing the understanding of plate tectonics through their pioneering work in mapping the ocean floor. Here's how their work contributed to the theory:
1. **Creation of Ocean Floor Maps**: Heezen was collecting bathymetric (depth) data of the ocean floor, while Tharp, who was trained as a geologist and cartographer, interpreted these data to create detailed maps of the ocean floor. They worked together at the Lamont-Doherty Earth Observatory of Columbia University.
2. **Identification of the Mid-Ocean Ridge**: Tharp identified a continuous mountain range in the middle of the Atlantic Ocean through the bathymetric data. This would later be recognized as part of the mid-ocean ridge system, which encircled the Earth like the seams of a baseball, and it proved to be a central feature in the process of sea-floor spreading.
3. **Discovery of the Rift Valley**: Tharp's work also led to the discovery of a deep canyon, or rift valley, along the crest of the mid-ocean ridge. This was critical evidence for the theory of sea-floor spreading, as it suggested that new oceanic crust was being formed along the mid-ocean ridge and then moving away from it.
4. **Support for Sea-Floor Spreading**: Tharp and Heezen's discovery of the rift valley provided strong support for Harry Hess's hypothesis of sea-floor spreading, proposed in the early 1960s. Hess postulated that new ocean floor was being created at the mid-ocean ridges and pushed away to the sides as more new material surfaced, a key mechanism that would later be incorporated into the theory of plate tectonics.
5. **Links to Earthquakes and Volcanism**: Heezen, initially skeptical of the idea of continental drift, eventually came around to the idea after noticing that earthquake epicenters lined up remarkably well with the rift valleys mapped by Tharp. This provided geological activity evidence that supported the dynamic movement of the Earth's crust.
6. **Publicizing and Recognition**: Although the significance of their work was not immediately recognized and female scientists like Tharp often faced tremendous sexism, their maps eventually garnered attention from the wider scientific community. One of Tharp and Heezen's maps famously became known as the "World Ocean Floor Map," which showcased the earth's underwater landscape and was published in 1977 with the National Geographic Society.
Their work was foundational in proving that the Earth’s lithosphere (crust and upper mantle) is broken into pieces, or plates, which are constantly moving. These findings, along with other lines of evidence from around the world, were fundamental in the acceptance of the theory of plate tectonics in the 1960s and 1970s, a theory that profoundly reshaped the understanding of Earth's geological processes.
Which of the following describes how marie tharp and bruce heezen found evidence that let to the theory of plate tectonics
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