Seafloor Spreading

Definition

Seafloor spreading is the process by which new oceanic crust is formed at mid-ocean ridges as tectonic plates move apart, causing magma from the mantle to rise and solidify. This mechanism not only generates new crust but also plays a crucial role in the dynamic nature of the Earth's lithosphere and the cycle of plate tectonics, influencing the evolution of ocean basins and the distribution of continents over geological time.

5 Must Know Facts For Your Next Test

1. Seafloor spreading was first proposed by Harry Hess in the early 1960s, based on evidence from ocean floor mapping and studies of magnetic anomalies.
2. As new oceanic crust is formed at mid-ocean ridges, older crust is pushed away from the ridge, leading to an increase in the age of the ocean floor as you move farther from the ridge.
3. The process of seafloor spreading is accompanied by volcanic activity and earthquakes along mid-ocean ridges, which are critical features of divergent plate boundaries.
4. The age and thickness of sediments on the ocean floor provide key evidence for seafloor spreading, as sediments become thicker and older with increasing distance from mid-ocean ridges.
5. Seafloor spreading contributes to continental drift by altering the arrangement of continents over geological time, influencing climate patterns and ecosystems.

Review Questions

• How does seafloor spreading contribute to the formation of oceanic crust and what are its implications for plate tectonics?
  • Seafloor spreading contributes to oceanic crust formation by allowing magma from the mantle to rise at mid-ocean ridges as tectonic plates diverge. This process continuously creates new crust while simultaneously pushing older crust away from the ridge. The implications for plate tectonics are significant, as this mechanism drives the movement of tectonic plates and influences various geological phenomena, such as earthquakes and volcanic activity.
• Discuss how magnetic reversals support the theory of seafloor spreading and provide evidence for plate tectonics.
  • Magnetic reversals provide critical evidence for seafloor spreading through the pattern of magnetic stripes found on either side of mid-ocean ridges. As magma solidifies at these ridges, it records the Earth's magnetic orientation at that time. When magnetic reversals occur, new magma will record a different orientation, creating symmetrical patterns on either side of the ridge. This observation supports plate tectonics by demonstrating how oceanic crust has formed over time and provided a timeline for plate movement.
• Evaluate the impact of seafloor spreading on continental drift and how this process has shaped Earth's geological features over millions of years.
  • Seafloor spreading has a profound impact on continental drift by continuously generating new oceanic crust, which influences the arrangement of continents. As ocean basins expand due to this process, continents can shift position, leading to changes in climate, sea level, and biodiversity. Over millions of years, these shifts have resulted in significant geological features such as mountain ranges and deep-sea trenches. By understanding seafloor spreading, we can better appreciate how Earth's surface has transformed throughout its history.

Related terms

Mid-Ocean Ridge: An underwater mountain range formed by plate tectonics, where seafloor spreading occurs as magma rises to create new oceanic crust.

Plate Tectonics: The scientific theory explaining the movement of the Earth's lithosphere, composed of several large plates that glide over the semi-fluid asthenosphere.

Magnetic Reversal: The phenomenon where the Earth's magnetic field changes direction, which can be recorded in the rock as seafloor spreading occurs, helping to date and track the movement of tectonic plates.