Introduction & Geological Background

Welcome to Alexander Falls! Located in the scenic Callaghan Valley, this impressive 43-meter (141-foot) waterfall is a stunning showcase of the dynamic geological forces that shaped southwestern British Columbia.

The landscape here is a classic product of volcanism and glaciation—often referred to in the region as the "Fire & Ice" dynamic.

1. The Volcanic Foundation: Cheakamus Basalt

As you look at the waterfall, you are observing water cascading over stacked layers of volcanic rock. Specifically, Alexander Falls drops over multiple distinct layers of Cheakamus basalt.

• Basalt is an extrusive igneous rock formed from low-silica, fluid lava flows that cooled relatively quickly on the Earth's surface.

• In the Callaghan Valley, volcanic activity from nearby volcanic fields (such as the Mount Cayley volcanic field) produced massive lava flows that filled valleys and cooled into thick, blocky, and sometimes columnar-jointed basalt layers.

2. The Power of Water and Ice

The water plunging over the cliff is Madeley Creek, a major tributary of the Callaghan River.

• During the Pleistocene epoch, massive glaciers carved out the broad, U-shaped Callaghan Valley.

• As the glaciers retreated, they left behind steep topography and disrupted drainage patterns. Madeley Creek was forced to carve a new path over the resistant steps of layered basalt, creating the multi-tiered waterfall you see today.

• Differential erosion plays a major role here: softer layers or fractured zones between the basalt sheets erode faster than the dense basalt blocks, creating the stepped profile of the falls.

Logging Requirements

To claim this EarthCache as found, please visit the viewing platform at the coordinates, observe the geological features of the waterfall, and send your answers to the four questions below to the cache owner via email or Message Center.

You do not need to wait for a reply before logging, but logs with incorrect answers or without message submissions may be deleted.

Questions:

1. Rock Texture and Color: Examine the rock exposed around the waterfall (visible from the viewing platform or surrounding areas). Describe the color and surface texture of the basalt layers. Why do you think these rocks are dark in color?

2. Layers and Steps: Look closely at the cliff face over which the water falls. How many distinct major horizontal tiers or ledges can you identify as the water drops down its 43-meter descent?

3. Erosion and Flow: Madeley Creek constantly wears down the rock face. Based on the position of the water channel and the edges of the basalt layers, explain in your own words how the waterfall might change or retreat upstream over the next hundreds of years.

4. Optional Photo: Take a photo of yourself or your GPS device with Alexander Falls in the background and upload it to your log.