2026年3月托福机经套卷(第4套) - Read an Academic Passage Q4

Unveiling Earth's Core Geophysicists have long been intrigued by Earth's core (the center of Earth). When earthquakes occur, they send seismic waves through the planet, offering rare glimpses into this mysterious world. Interestingly, these waves sometimes slow down in unexpected ways, suggesting that the core's makeup may be more complex than just iron and nickel as previously believed. Some scientists suggest it might not be entirely solid, possibly containing molten layers or unusual elements that create a unique state of matter. Advanced computer models now depict the core not as a homogeneous sphere, but as a layered structure with distinct regions. These models also propose phenomena like super-rotation—where the inner core (the inner part of Earth's core) spins slightly faster than the rest of the planet—and directional differences in wave behavior, known as anisotropies. Collectively, these findings portray a core in constant motion. But is this picture complete? Some researchers argue that these models rely on overly simplified assumptions. Truly understanding the inner core demands cutting-edge technology and fresh perspectives. The limitations of current theories remind us that the deeper we explore planetary science, the more we challenge our understanding of it.