Sometimes at Ask-a-Geologist, we get off-the-wall questions that open up all sorts of interesting possibilities.They are hard to resist falling into the deep water over... Please bear with me on this longest of chapters, but I promise it's full of fascinating stories!
Q: Question - the best place for a geology vacation? Not including
the Grand Canyon. Already been there.
- Brett B
A: I can think of several cool possibilities for a
"geologic vacation."
If you have the resources, a trip to the United Kingdom
would be educational. Virtually the entire geologic time scale from the
Precambrian to the Holocene is represented if you walk from northern Scotland
to Surrey. The first geologic maps were created here ~150 years ago, and you
can find many place names that gave the geologic time-scale its epoch names: Cambrian (Cambria),
Ordovician, Silurian, Devonian (Devon), etc. Actually, the Ordovician was named after a Celtic tribe called the
Ordovices, and the Silurian period was named after a Celtic tribe of Wales, the
Silures. By the way, it's easy when you are driving between England and Wales to know when you make the transition: as you enter Wales you will see a sign with the red dragon Uther Pendragon symbol - and English signs with Welsh graffiti on them. Also, the peaceful pastoral countryside of England suddenly gives way to wild, hilly and incredibly beautiful Wales.
If you live in the southwestern US, you can try the Tucson,
Arizona, area. There are rocks ranging from the Precambrian to the Holocene nearby,
with some great Mesozoic fossils. If you stand in downtown Tucson and look
north, you can see apparent sedimentary layers in the Catalina Mountain front - get up
close and you can see that yes, these were once sedimentary rocks, but are now converted
to Augen gneiss by deep burial (at least 7 km deep) followed by uplift. The
most amazing fossil in history - at least in my opinion - was found north of this mountain front. As
you move farther and farther north in that range you will see the gneiss gradually turns
to a classic granite, representing deeper and deeper burial of the original
sedimentary rocks... but a recognizable
crinoid head was found in those rocks
at the transition point by Dr Ed McCullough, at one time the department of geology head at the nearby University of Arizona. This was a Mesozoic fossil in granite! There is also a wide
range of mines you can visit, including giant Sierrita, Mission, and Silver Bell porphyry copper mines, as well as
disseminated gold and silver mines.
Probably the most visually captivating place is
Bisbee, Arizona, near the Mexican border. The old Copper Queen porphyry copper
mine is long closed, but the rock samples you can find in little gem and
mineral shops in the town are amazing. Bisbee has an odd flavor of cowboys and aging hippies, and some truly funky Bead and Breakfast places. Tombstone, Arizona, lies north of there, with
it's historical gold mines and hard-to-find real Boot Hill, and easy-to-find fake Boot Hill cemeteries.
Drive west from
Bisbee and you will reach Sierra Vista and the US Army's active Fort Huachuca military base, where the 19th Century Buffalo Soldiers (African-American Cavalry) once trained, and where the Predator drones were originally developed and tested. On your way you will see on your left, just
inside Mexico, an austere mountain range called the Sierra San Jose. Until we (several US Geological Survey geologists) got there
in 2000, this range had never been geologically mapped before - a very
unusual thing for this day and age. We could see communications towers on the top - but could find no roads up to them. In conversations with a local rancher, we learned that obreros - Spanish for "worker" and really tough guys - had carried the components on their backs all the way up the rugged, Manzanita-covered slopes. The 16-km-long (10-mile) mountain range consists of a large stack of Mesozoic sediments uplifted
by a huge granite pluton, fragments and cupolas of which you can find around its flanks. On the west side lies a town, located on the banks of the Mexican part of the San Pedro River, named "Difunto" - Spanish for "dead". Halfway up the north side of this strange mountain range there is, inexplicably, a small shrine to La Virgin. It was only a meter tall, made of cement blocks, stucco, and and lovingly-applied white and blue paint, with a small metal gate opening into an interior where we could see a small statue of the Virgin Mary with some votive candles. The last time we were there, doing a mapping traverse up the rugged north flank, we found a small offering at La Virgin's feet: a plasticine bag with white powder in it. We didn't spend a lot of time there.
Why were we working here? Because the San Pedro River crosses the international frontier and hosts one of four major North American migratory bird flyways. In fact, the American side has been made into the San Pedro National Riparian Area to preserve this flyway from ever-increasing demands on groundwater. As part of my work, I arranged for a Canadian aircraft to fly a powerful electromagnetic surveying system over the San Pedro Basin. We covered about 1,000 square kilometers (~400 square miles) on the American side alone, and then used other ground-based geophysical methods to map the water on the Mexican side. I could "see" where the groundwater lay down to 400 meters (~1,200 feet) depths, and could show how it influenced and controlled the surface water in the San Pedro River flowing above it. If the river was ever allowed to dry up because of excessive withdrawal of groundwater in this desert area, then this zone of incredible biodiversity (15 species of hummingbirds have been seen in the Huachuca Mountains alone) would disappear forever.
I currently live in the Pacific Northwest, where the geology
is pretty much all volcanics, all the time. This includes, but is not limited
to, the massive 15-17 million-year-old Columbia River Flood Basalts that cross the entire
state of Washington and cover most of eastern Oregon. Estimates of the volume of this massive eruption range up to 175,000 cubic kilometers (42,000 cubic miles!). The Cascades Range both predates and post-dates this immense flood basalt episode, and is made up of subduction-plate-related volcanoes. The down-going Juan de Fuca oceanic crustal plate is being over-ridden by the Western North American continent, and as the down-going plate partially melts it gives rise to a string of parallel volcanoes above the melt zone. If you are fascinated by volcanoes, this is the place to visit, and Mount
St Helens National Volcanic Monument should be high on your list. Visit first
the Johnston Ridge Observatory on the north side, named for one of our
geologists killed there in the 1980 eruption, and learn the startling history
of this most active of all of the Cascades volcanoes. Then take the two hours
necessary to drive around to Ape Cave on the south flank - it's the longest and
best-preserved lava tube in the United States. Bring at least two flashlights,
and a bike helmet if you want to climb the technical upper half of the tube (I
have a permanent dent in my forehead from making a right turn into a basalt
blade).
Perhaps even more sobering is to drive through the spectacular Columbia River Gorge. If you travel on the Washington State side, be sure to stop and
climb Beacon Rock. This is a 57,000-yr-old volcano core, standing nearly 300 meters tall - a huge pillar of columnar basalt sitting on the edge
of the Columbia River, like a giant human thumb sticking out of the water's
edge. There is a wonderful walkway - with guard rails - all the way to the top,
where you get an awesome view. You can see Bonneville Dam to the east, where ocean tides reach nearly 200 km from the Pacific Ocean. You can look beyond and see part of the Bridge of the
Gods - a still on-going, ginormous landslide. Beacon Rock was a once-conical volcano, but had all
the tephra and lava on its flanks stripped off when ~5,000 cubic kilometers of
debris came roaring down the Gorge in late prehistoric times. These are the largest
water floods ever recorded in the geologic record, possibly excepting the filling of the Black Sea ~7,000 years ago. These truly catastrophic floods were caused when the Missoula Ice Dam
broke open about 12,000 years ago (and up to 71 subsequent
times). You can find boulders on the Oregon side that are the size of a VW van
- that have been lifted up over a 400-meter-high ridge and dropped on the other
side by this barely imaginable event. It's an amazing place to visit, and
spectacularly gorgeous any time of the year. The flood debris filled the canyons in what is now modern Portland, Oregon, and then rushed out past modern Astoria into the Pacific Ocean. Bathymetry has imaged a gargantuan debris pile to the southwest of the Columbia River mouth.
If you're an American, it's probably not wise to visit
Venezuela right now. There is a great deal of political animosity between the two governments, even though the Venezuelan people are irrepressibly buoyant and kind. More to the point, the crime rate in Caracas may be the highest in the western hemisphere. However, once past the capital Caracas, you enter a truly mesmerizing world. The strange Imataca Formation south of Puerto
Ordaz (where I lived for three years) host among the most ancient rocks on the planet, thought to be 3.4 to 3.7
billion years old - second only to those in western Australia. Cross south into the "merely"
1.75-1.9 billion year old Pastora province, and you are in a jungle world of
gold and diamonds - and 4-meter crocodiles and four different species of piranha.
Farther south still you will arrive at the strange Gran Sabana - literally Great Sheet. At the junction of Brazil, Guyana, and Venezuela you will find the eery Mount Roraima, the "Mother of
Waters" standing up out of the Gran Sabana. This is a huge Tepui, or flat-topped mesa-like mountain, surrounded by
700-meter cliffs and waterfalls on all sides. It's about 3,000 meters high, and the rocks are
~1.7 billion year old quartzite. Break off a piece and it looks like rough sugar cubes. Consequently, very little can grow on it - and the vegetation that does is highly adapted, dominated by Pitcher plants and Venus Fly-Traps genetically designed to capture their nutrition from the insects blown in. Some 40% of the vegetation here is found nowhere else on Earth. Until the late 19th Century, nine
failed expeditions were mounted to reach the top, where scientists thought there might
still be dinosaurs preserved by the profound cliff-surrounded isolation. The 10th expedition finally made it to the top of what became the inspiration for Sir Arthur Conan Doyle's book "The Lost World". From
the top of this enormous Tepui, you can see diabase dikes that filled cracks in the crust when the
Atlantic Ocean opened up the first time. They look like dark snakes made up of
of trees crossing the otherwise nutritionally-starved Gran Sabana below you. There are diamonds and gold
in abundance in most of the rivers west and north of Mount Roraima. The mountain and
a nearby Tepui that is even larger (Auyantepui) figured in the movie
Arachnophobia. If you have ever climbed Mount Roraima (or Kukenan, its nearby
sister), you will understand what inspired the Halleluja Mountains of the
movie Avatar.
Why were we working here? In pre-Chavez days, the US Geological Survey was asked to send a resident team - a scientific mission that I headed - to map the southern half of the country and help assess the mineral resources there. Venezuela was already endowed with one of the largest hydrocarbon resources in the western hemisphere, but it doesn't take a rocket scientist to realize that the sweet crude will not last forever (the production decline has been accelerating since Hugo Chavez took power and stopped maintaining the infrastructure). When we arrived we understood the problem: the southern half of Venezuela at the time was nearly completely covered by jungle - the northern tier of the great Amazonas forest - and was nearly inaccessible except by helicopter and dugout canoe. There were no maps - and only one road on the eastern edge. In three years we produced the first complete digital base map and the first geologic map of the area, along with an astounding mineral resource assessment. If Venezuela was blessed with vast hydrocarbon resources, then its hard mineral wealth - gold and titanium and diamonds and Rare-Earth Elements - dwarfed even that. The terrible downside: uncontrolled "artisanal" miners have rapidly destroyed vast stretches of ancient forest, leaving holes of "agua negra" - still dark water that now breeds trillions of mosquitoes and now hosts truly dangerous, resistant-to-everything Falciparum Plasmodium - cerebral malaria.I was the USGS mission chief there, and to this day worry that I somehow contributed to this environmental destruction. The truth is that the government - probably no government - can control artisanal miners searching for gold and diamonds in a jungle.
Australia is also an amazing place to visit, with THE most ancient
rocks on the Earth (the Jack Hills of Western Australia, where a single zircon grain is thought to be 4.4 billion years old). Australia also hosts THE largest
gold-uranium-copper mine on the planet (Olympic Dam). It was found when geologists visited a rancher, asking about odd colors in surface rocks. The rancher said no, but he showed them a bucket he used to draw water from a well - and it had become copper plated! Nearly everything on this continent is unusual, starting with the highly-evolved, mostly marsupial wildlife. Because the continent is
both stable and largely exposed, with little vegetation beyond the eastern
eucalyptus forests, virtually all the large asteroid impacts are preserved to
some degree and visible. Before he died, Gene Shoemaker spent every Australian
winter here for years, mapping these structures. He and his wife Carolyn were
trying to get a sense of what the real impact history of the entire Earth was -
by counting the impact structures on this very stable and most ancient
continental craton.
Why were we there? The US Geological Survey has sent scientist to visit and learn, periodically. However, I have been there many times simply because my oldest daughter and her husband are university professors in Sydney, and two grandsons come with the package.
The Arabian Peninsula hosts late Precambrian rocks - the
Arabian-Nubian craton was split by the Red Sea 35 million years ago, and then again starting about 5 million years ago. A strange string of huge, north-trending basalt-andesite fields locally called "Harrat" and passing through modern Makkah, are thought to represent an incipient rift opening up - like a new Gulf of Aqaba. You would just have to wait around for another 5 million years. The eastern part of the country is made up of Paleozoic rocks, and they host the largest single oil field on Earth, the famous Ghawar. According to the Bible, King
Solomon's gold came from "Ophir" - which apparently consisted of 872 "SAMs" - small
ancient mines - scattered throughout the Precambrian part on the west of the
peninsula. The northern reaches of the Arabian peninsula, shared with Jordan and Iraq, were once the ancient Mesozoic Tethys seaway, and host a huge phosphate resource - the remains of fish who once lived in this ancient sea. If you do a gamma-ray sounding, you will find uranium intimately associated with the phosphate. Map the uranium in 3D and you have mapped the un-weathered part of this immense phosphate deposit. This northern terrain, especially around the towns of Ar-Ar and al-Jalameed, rival the Nullarbor Plain of western Australia for absolute, stupefying flatness. It is as flat as you could possibly imagine for hundreds and hundreds of kilometers in all directions. We had to use GPS units to keep from accidentally straying across the international frontiers while we lived and worked in this vast region. A pair of interesting anecdotes: about 2 out of every three drill-holes started in this vast region lose (and then cannot recover) their fluid circulation - and the nights are filled with bats! Odd combination? Not if the land is a giant Karst (cave) terrain covered with a thin veneer of loess! All the loess appears to have been blown into the region from the Sahara desert of north Africa to the west - yes, it crossed the 200-km-wide Red Sea. I once flew to Ar-Ar and the Boeing 737 aircraft couldn't land - the pilot could not see the ground, which was enveloped in a 3-day sandstorm of Biblical proportions. The famous Wabar asteroid impact site - similar to the Sedan nuclear
test crater (Nevada Test Site) in all respects save there is no radioactivity - is found deep in
the Empty Quarter. We have calculated that a 30-meter (100-ft) iron-nickel asteroid hit here in 1863 with the kinetic energy release of a Hiroshima-sized atom bomb. When I first visited the site and absorbed the geologic evidence, the hair stood up on the back of my neck. We believe the Bedouin first found it because their grandfathers witnessed the stratosphere-height mushroom cloud that the geologic mapping said it caused. This cloud dropped a rain of molten glass almost a kilometer northwest of the impact site. The 'Rub al-Khali, as this desert is known in Arabic, is the largest
contiguous sand dune desert on Earth. The temperature measured 1.5 meters off
the ground in May 1995, using a calibrated thermometer while I did a magnetic survey there, reached 61C (142
F). Despite the forbidding logistics - it's probably easier to cross Antarctica
where aircraft can actually land - this site has been visited many times (an article I wrote about it can be
found in the
November 1998 Scientific American issue). Did I mention the Red Sea enough? This modern rift hosts, on its eastern margins, the ancient Frankincense Trail, which followed where the wells were. The wells are found at the base of the 35-million-year-old Scarp, a 2,500-meter-high (8,000-ft) wall that intercepts passing clouds and draws their moisture down to a string of wells following its 1,000-km-long (600-mile) base. So: geology controlled one of the most important trade routes of the ancient world.
Why were we there? In 1934 King Abdul-Aziz, who united the peninsula and founded Saudi Arabia, invited a US Geological Survey hydrologist named Glen Brown to help them find additional water resources for his parched desert kingdom. For 60 years there was a USGS office in Jeddah, located on the Red Sea, and we mapped the geology and mineral resources of the western and northern parts of the country at the request of its government. In 1996 this science mission became the Saudi Geological Survey, modeled after the USGS. For four years I was the USGS deputy mission chief there.
I hope this gives you at least an idea of where you might
want to take a geologic vacation. I have some experience with Africa and Asia,
but not sufficient to advise you about these places. Kamchatka (Russian Far
East) has some truly amazing and VERY active volcanoes, but is probably harder
to get to for the ordinary tourist than Antarctica. A surprisingly large number
of people there speak English, but a limited ability in Russian goes a long
way. Chile is easier to get to, with equally fascinating
volcanoes, but large parts of the country are Spanish-speaking ONLY.
~~~~~
