Convergent Boundary: When Earth's Plates Collide — Passage and Quiz

The Earth's tectonic plates are constantly moving, and when they push together, they form convergent boundaries. These collisions create some of the planet's most dramatic landscapes, from towering mountain ranges to deep ocean trenches. There are three main types of convergent boundaries, each producing unique geological features.

1. Oceanic-Continental Collision

When an oceanic plate (denser) slams into a continental plate (less dense), the heavier oceanic plate is forced beneath in a process called subduction. This creates deep trenches and violent volcanoes along the edge of the continent. The Andes Mountains in South America formed this way, as the Nazca Plate subducts beneath the South American Plate, fueling eruptions like Mount St. Helens.

2. Oceanic-Oceanic Collision

When two oceanic plates collide, the older, denser plate sinks, forming a subduction zone. This creates volcanic island arcs and the deepest trenches on Earth. The Mariana Trench, the deepest point in the ocean, was formed by the Pacific Plate diving beneath the smaller Mariana Plate. Nearby, the Mariana Islands are a chain of volcanoes built from melted subducted rock.

3. Continental-Continental Collision

When two continental plates collide, neither sinks easily because they are both lightweight. Instead, the crust crumples upward, forming massive mountain ranges. The Himalayas, home to Mount Everest, are still rising today as the Indian Plate smashes into the Eurasian Plate at about 5 cm per year.

These collisions don’t just build mountains—they also trigger earthquakes and volcanic activity. By studying convergent boundaries, scientists better understand how Earth’s surface evolves over millions of years.

Fun Fact: Did you know the Himalayas are still growing taller every year? Thanks to the ongoing collision between India and Eurasia, Mount Everest rises about 4 mm annually—that’s roughly the height of a pencil eraser!