GEOLOGY

Detailed explanation-1: -Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor. Eventually, the crust cracks.

Detailed explanation-2: -Sonar advances continued during and after the Second World War. Sonar work led to the development of the first global map of the sea floor, which was published in the 1960s. This information was very important in developing the geologic theory of plate tectonics.

Detailed explanation-3: -Why was the discovery of marine magnetic anomalies so important to the theory of seafloor spreading? Because they show an accurate record of the creation and movement of oceanic crust.

Detailed explanation-4: -Multibeam sonar systems were developed to produce more accurate maps of the seafloor. In a multibeam sonar system, the sound energy from the transducer is emitted in the shape of a fan that spreads downward to the seafloor. The area of the seafloor ensonified is called the swath.

Detailed explanation-5: -Scientists discovered that as they moved away from the mid-ocean ridge, the samples of both the crustal rock and sediments on the ocean floor increased in age. The newest, youngest rock was closest to the mid-ocean ridge. This evidence supported the theory of seafloor spreading.