Erosion is an event that happens daily on Earth, but it happens very slowly. Erosion is the movement of the broken down materials from weathering. The dirt, plant matter, rocks, and other materials are moved to a new location, and new landforms are created while others are destroyed or changed.

Erosion is an extremely slow process, but the results are extraordinary. The clues in the text that let readers know this is a slow-moving process is "slowly," "were a towering mountain range millions of years ago," "erosion over time," and "used to be." These words and phrases all hint to something taking a long time to happen. Some processes on earth happen quickly, but not erosion!

The photo that shows a slowly occurring Earth event would be the cliffsides of a beach. These have been worn away over many years (millions) as the dirt, sand, and rocks eroded. Lightning strikes, tropical storms, and wildfires are all quickly occurring events.

The provided photo depicts a stream or river racing through a carved out section of a canyon. This process is called weathering and erosion and takes millions of years to happen. The river beating into the sides of the canyon breaks apart small pieces of rock and sand, and the water pushes it downstream. The results are a carved section with deposits of debris downstream.

Weathering is the process of breaking down or wearing down the Earth with wind or water. As rivers move through areas banks and canyons are formed. Wind and rain beat on the cliffsides and cause pieces to break away. These are examples of the slow-moving process of weathering.

In the passage given, the event that happened slowly was the mudslide. Events on Earth can happen at different speeds. The wildfire is described as "sudden," "didn't rage for long," and "a flick of a match" can start them. This is all language that shows how quickly the fire started. The mudslide, on the other hand, is described as happening after "heavy rain for days," and that "years of erosion" led to the right conditions. The text also states that the mudslide is "still ongoing" and that "when land is broken down over time," conditions become more dangerous. This demonstrates an event that takes a long time or happens slowly.

Cliffsides are formed over thousands, if not millions of years of weathering and erosion. Waves, wind, rain, and possible vegetation and ice wear away the rock and break it over the years. Water and wind carry the broken pieces away to new places. This is a very slow-moving process.

Volcanic eruptions, landslides, earthquakes, and tsunamis are all events that happen quickly. Events that occur slowly are weathering and erosion, creating new landforms. The keywords that let readers know this event does NOT occur slowly are "sudden" and "very little time or warning."

Erosion is the movement of broken materials, and only once answer choice mentions moving the pieces, "A river carrying broken rocks downstream." This example shows that water in the form of a river is moving the broken parts of the material. The other examples are weathering, which is the process of breaking the materials.