What did scientists observe in the ocean floor which indicates that the Pacific Ocean is becoming smaller?(1 point) Responses spreading spreading continental drift continental drift subduction subduction plates floating on the mantle
subduction
The correct answer is: subduction
To understand why scientists believe that the Pacific Ocean is becoming smaller, one must consider the concept of plate tectonics and the movements of Earth's tectonic plates. Here's an explanation of how scientists observe these movements and interpret them:
1. Spreading: At mid-ocean ridges, new crust is formed as molten material rises to the surface and pushes the existing plates apart. This process is called seafloor spreading. Scientists can measure the rate at which new crust forms and spreads, allowing them to gauge whether the ocean is expanding or contracting.
2. Continental Drift: The theory of continental drift suggests that Earth's continents are not fixed but constantly moving. Over geologic time, continents can collide or drift apart. When continents move apart, they create gaps or rifts that can be observed on the ocean floor.
3. Subduction: Subduction occurs when one tectonic plate dives beneath another plate, usually forming deep ocean trenches. In the case of the Pacific Ocean, subduction zones are prevalent, such as the infamous "Ring of Fire." When tectonic plates subduct under another plate, it indicates that the ocean is shrinking.
4. Plates Floating on the Mantle: The Earth's lithosphere is broken into various tectonic plates that float on the semi-fluid asthenosphere in the mantle. The movement of these plates is what causes geological events like earthquakes, volcanic eruptions, and the reshaping of the ocean floor.
By studying the above processes using techniques like seismic imaging, measuring plate movements using GPS, and analyzing changes in magnetic anomalies on the ocean floor, scientists can observe the interactions between tectonic plates and infer whether the Pacific Ocean is expanding or contracting. The presence of subduction zones, the movement of continents, and the measurement of spreading rates all contribute to the understanding that the Pacific Ocean is becoming smaller.