Pahvant Butte: Lace Curtain 🎦 EarthCache

To log this Earthcache, you will NOT be looking for a typical geocache container (in fact, there IS no container to find). Rather, to prove you were here and learned something you'll need to find the answers to the given questions (found below as well as at the end of this description), which you will then email me, the owner (this is the same process for ALL Earthcaches).

So go ahead and log your experience while here, submit photos, etc., but email your answers to me (not in your visit log) to get credit for "finding" this cache. If it seems too complicated, don't sweat it too much (as long as I can see that you made an honest effort to answer all of the questions, that is fine). Remember that the purpose of this is to learn something, and most importantly, to have fun! Also, feel free to email me with any questions you may have, I'd be happy to help.

Special thanks goes to Teresa Frampton, the Outdoor Rec Planner at the BLM office in Fillmore, who generously gave permission for this earthcache to be created and placed.

To log this cache, use the info below, your surroundings, observations and logic to answer the following questions. Email me the appropriate answers (don't post them in your log, or per Earthcache guidelines your post will have to be deleted), and most of all, have fun!

1. What created the steep cliffside seen here at the Lace Curtain site, according to the description info?
2. Next, observe the cliffs, as well as the base; then describe the texture, color, and composition of the stone here. Based on your observations, which of the two theories seems most likely? Explain why.
3. (Optional): Take and post a picture of yourself and / or the Lace Curtain in the online log.

Sentinal of the Black Rock Desert

This area, known as the Black Rock Desert (volcanic field) was once a hotbed for volcanic activity, as other nearby sites indicate. This volcanic field covers over 2,700 square miles, from as far away as Topaz Mountain (with its interesting rhyolite deposits containing topaz and red beryl) to the Obsidian Fields found to the SW, and also Tabernacle Hill, a dormant volcano known for its fantastic lava tubes to the SE.

Image: Here we see the lava tubes nearby Tabernacle Hill, another interesting sight found in the Black Rock Desert

Pahvant Butte

This butte is actually a dormant volcano, specifically a cinder cone volcano, and it hasn't been dormant all that long, geologically speaking. In fact, 16,000 years ago, Pahvant Butte was mostly underwater, in the middle of what we now call Lake Bonneville, an ice-age lake formed by the melting of immense glacial deposits across the Intermountain West. However, volcanic activity has been the norm here for millions of years, and about 15,500 years ago, a violent eruption took place. Something akin to the 1963 Surtsey Eruption near Iceland likely occurred.

Image: Here the 1963 eruption of Surtsey occurs in the Atlantic Ocean, a sight similar to what created the current Pahvant Butte
(source: wikimapia.org) 

The Death of a Volcano

While the volcano here already existed as a small island, this explosive event was a real barn-burner. It set off a tsunami-like wave that raced violently across the lake, and plumes of basalt lava shot high in the sky, then quickly cooled into small glassy particles (i.e. volcanic ash), and larger gravelly pieces (aka volcanic cinders), which together are known as tuff. 

The explosion was so powerful, it produced an immense crater on the south side of the butte (still visible today), and covered the rest of the butte / volcano in an immense layer of the new tuff. This joined the many other layers of tuff that had developed with previous eruptions, and afterwards the Pahvant Butte returned to dormancy...for now.

The "Lace Curtain"

At the North end of the butte, there is a sheer cliff, filled with strange looking formations called colloquially the Lace Curtain. While the giant explosion left Pahvant volcanically dormant, the forces of erosion and weathering did not halt. The North Face of the butte was especially exposed to the erosional effects of Lake Bonneville's waters, and over the following years, the waves beat mercillesly on the solitary tuff cone island that rose up out of the waters. As time passed they cut a straight cliff face into the north side of the cone, yet other processes were also at work.

Image: Here is an illustration of the butte (source: geology.utah.gov)

The many layers of tuff that had formed over many eruptions made up the layers of the butte, and as the cliff was being created, groundwater seeped deep into the tuff. Wherever the butte was above the water (at this time the water was at the higher, Bonneville level), the surface of the tuff was gradually transformed by groundwater into a yellow-brown glassy substance known as palagonite. Below the Bonneville level, the surrounding tuff did not undergo this transformation, and remained a black color.

Cementation Theory: Deep inside the butte, the tuff was also affected by the groundwater, as it seeped deeper and deeper. Gradually, as tiny channels of water worked their way through the tuff, they turned it whiter as the water combined with the tuff and became patially cemented. Then, as the cliff face was eroded, the softer, uncemented but now exposed material was worn away. While Lake Bonneville eventually dried up, the wind continued to do its work, resulting in the strangely beautiful Lace Curtain that can be seen here today.

Eruption Theory: Another source I found made a different claim as to the origin of the Lace Curtain. This source stated that about 15,500 years ago, molten lava erupted and flowed down the cliff face here, and was quickly cooled and seemingly "frozen" in place by the moisture from Lake Bonneville.

So which theory is correct? Take a look around, and decide for yourself, and thanks again for visiting!