Understanding Harry Hammond Hess and Geological Hypotheses

The question asks about a specific hypothesis proposed by the geologist Harry Hammond Hess in 1962. This requires knowledge of significant contributions to the field of Earth science, particularly concerning the movement of continents and the ocean floor.

Harry Hammond Hess and Sea Floor Spreading

Harry Hammond Hess was a pivotal figure in the development of plate tectonic theory. His work in the early 1960s provided crucial evidence that supported earlier ideas about continental movement.

In 1962, Hess published his groundbreaking paper titled "History of Ocean Basins." In this work, he proposed the concept of sea floor spreading. This hypothesis suggested that the ocean floor is created at mid-ocean ridges, where molten material (magma) rises from the mantle and solidifies to form new oceanic crust. This new crust then moves away from the ridge in both directions. The older crust is eventually consumed at deep ocean trenches, where it is subducted back into the mantle.

The sea floor spreading hypothesis provided a mechanism for continental drift, explaining how continents could move across the Earth's surface as part of larger lithospheric plates.

Analyzing the Given Hypotheses

Let's look at the other options provided:

• Continental Drift hypothesis: This hypothesis was famously proposed by Alfred Wegener in 1912. It suggested that the continents were once joined together in a supercontinent (Pangaea) and have since drifted apart. While related, it was proposed much earlier than 1962 and by a different scientist.
• Gaia hypothesis: This hypothesis, primarily developed by James Lovelock in the 1970s (later with Lynn Margulis), proposes that living organisms and their inorganic surroundings have evolved together as a single, self-regulating system. This is a biological and environmental hypothesis, not directly related to the geological processes of the Earth's crust propounded by Hess.
• Geographical cycle hypothesis: This concept, developed by William Morris Davis in the late 19th and early 20th centuries, describes the evolution of landforms over time through erosion. It's related to geomorphology, not the large-scale movement of the Earth's crust proposed by Hess.

Comparing the options, the hypothesis specifically propounded by Harry Hammond Hess in 1962 is the Sea floor spreading hypothesis.

Based on historical geological research and the timeline provided, Harry Hammond Hess is credited with formulating the Sea Floor Spreading hypothesis in his 1962 publication.

Revision Table: Key Geological Concepts

Additional Information: Impact of Sea Floor Spreading

The Sea Floor Spreading hypothesis was revolutionary because it provided a plausible mechanism for how continents could move, something that was missing from Wegener's original Continental Drift hypothesis. Evidence like the magnetic striping of the ocean floor, the age of oceanic crust increasing away from ridges, and the distribution of earthquakes and volcanoes strongly supported Hess's ideas.

Sea floor spreading, combined with the concept of continental drift and other geological observations, ultimately led to the development of the comprehensive theory of Plate Tectonics in the late 1960s. Plate tectonics is now the unifying theory in geology, explaining most large-scale geological phenomena on Earth.