What type of movement do internal forces like plate tectonics cause?

Internal forces, specifically the movements associated with plate tectonics, are primarily responsible for geological phenomena such as earthquakes and volcanic eruptions. The Earth's lithosphere is divided into several tectonic plates that float on the semi-fluid asthenosphere beneath them. As these plates move, they can interact in various ways at their boundaries: they might collide, pull apart, or slide past each other. These interactions can generate significant stress within the Earth’s crust, leading to the abrupt release of energy in the form of earthquakes.

In addition to earthquakes, the movement of tectonic plates can also lead to volcanic activity. When plates diverge, magma from the mantle can rise to fill the gap, creating new volcanic islands or underwater volcanoes. On the other hand, when plates converge, one plate may be forced down into the mantle, leading to melting and the formation of magma that can eventually result in volcanic eruptions.

The other choices do not directly relate to the impacts of internal forces. Weather changes are primarily influenced by atmospheric conditions rather than tectonic activity. Changes in human population density are influenced by socio-economic factors and environmental conditions, not by the movements of tectonic plates. Water flow changes can be affected by various factors, including climate and human activity, but