Final answer:
Tectonic activity impacts sea level through the movement of tectonic plates, which can elevate or depress the sea floor, thus displacing water and changing sea levels. It also influences mountain building and isostatic adjustment, which affect local sea levels.
Step-by-step explanation:
Understanding how tectonic activity impacts sea level requires a look at the Earth's dynamic processes. The movement of tectonic plates, which make up the Earth's crust over a molten iron core, is influential in shaping the planet's surface and oceans. These plates can diverge, converge, or move alongside one another. When plates diverge, magma rises to fill the gap, creating new crust that can elevate the sea floor and displace water, leading to an increase in sea level. On the other hand, the collision and subsequent subduction of one plate beneath another can form deep ocean trenches, changing the volume of the ocean basin and potentially affecting sea levels.
Additionally, tectonic activity is often associated with mountain building. Mountains can change regional climate patterns and water storage on land, which in turn can influence sea levels. The rising and falling of land masses, also a result of tectonic movement, can alter local sea levels. Moreover, the weight of large ice sheets during ice ages can depress the Earth's crust. As these ice sheets melt due to global warming, the crust slowly rebounds, a process known as isostatic adjustment, which can cause localized changes in sea levels.
It is clear that tectonic plate activity is intimately linked with the geography of our planet and has a significant influence on sea level, directly through the movement and changes in the sea floor topography and indirectly by affecting climate and ice distribution.