Surge Channel and Vesicular Bubbles EarthCache

Surge Channel and Vesicular Bubbles

Geologists maintain that the creation of this natural wonder of the Bay of Fundy began over three hundred million years ago, as a mountain chain created by the collision of two landmasses fractured the skin of the earth. One hundred million years later, after spending time as a warm shallow sea and then a large swamp, this region of Nova Scotia became the site of active volcanoes. Molten rock (lava) seeping up through cracks in the sandstone and shale of the developing coastline created basalt cliffs and the lava formations visible along the shore.

The phenomenal power of the Bay of Fundy tides is one of the great wonders of the world. About 160 billion tonnes of water flows through the Bay of Fundy each tide, equal to four times the estimated flow of all the freshwater rivers in the world combined. This tidal flow generates a 30 foot (10 meter) rise and fall of the water level. The tremendous amount of water causes regular coastal erosion.

Surge channel

At ground zero on the Bay of Fundy you will see a good example of a surge channel. The shape of the surge channel can be viewed at low tide and at high tide you can see the wave action in the channel.

A surge channel is a narrow inlet, usually on a rocky shoreline, and is formed by differential erosion of those rocks by coastal wave action. As waves strike the shore, water fills the channel, and drains out again as the waves retreat. The narrow confines of the channel create powerful currents that reverse themselves rapidly as the water level rises and falls, and cause violent hydrodynamic mixing.

The powerful waves at high tide can be seen surging up through the channel and spitting waves and rocks out. Surge channels can range from a few inches across to ten feet or more across. They may create tide pools if the conditions are suitable, but the rapid water movement typically creates a dangerous situation for people or animals that are caught by the current.

Vesicular Bubbles

The lava on the sides of the surge channel will show you a great example of vesicular bubbles. Looks like what moon rock might look like and one cacher said he called them worm holes.

Basalts are dark colored volcanic rock which contain many small holes most commonly vesicular. The drop in pressure that a magma experiences as it flows from underground to the Earth's surface allows water and gases in the lava to form bubbles over three hundred million years ago. If the bubbles do not get large enough to pop, they are frozen in the lava as vesicles formed by the expansion of a bubble of gas that was trapped inside the lava.

To log this Earthcache visit the viewing location. Please answer the following questions and send in a timely manner to my geocaching profile or email. Answers not received will result in deleted logs.

1. How long and wide is the surge channel?

2. Describe the bottom of the surge channel?

3. What is the diameter of a small and large Vesicular Bubble

4. Why are they different sizes?

5. Post a picture in your log with a personal item or hand in picture to prove you were there.

[REQUIRED] In accordance with the updated guidelines from Geocaching Headquarters published in June 2019, photos are now an acceptable logging requirement and WILL BE REQUIRED TO LOG THIS CACHE. Please provide a photo of yourself or a personal item in the picture to prove you visited the site.