Free levelled English reading practice. Read for meaning first, then use the full Speed Reading tool to time yourself and track your progress.
The theory of plate tectonics explains how Earth’s rigid outer shell is divided into moving plates. Earlier in the twentieth century, Alfred Wegener argued that continents had once been joined, but he lacked a convincing mechanism for continental drift. Mid-century discoveries transformed the debate: mapping revealed mid-ocean ridges, magnetic patterns recorded seafloor spreading, and global earthquake zones outlined plate boundaries. Plates diverge, converge or slide past one another, producing many earthquakes, volcanoes, mountain ranges and ocean trenches. The theory unified observations that had previously seemed disconnected and became a foundation of modern geology.
