If there was ever a tornado going on when a volcano is erupting…

Then there are questions that could only come from children who are learning, but haven't learned much, and have no fear about asking questions about things that are scarey/fascinating to them. The following "improbable" is actually not that far from the probable.

Q: Hello my name is Thorin and i have a question for my geography class.

If there was ever a tornado going on when a volcano is erupting, can the tornado, so to speak, pick up the lava erupting from the volcano. I hope you guys respond to my question.  Thanks, - Thorin T

A: Hi Thorin,

Tornadoes don't usually occur where there are volcanoes. Tornadoes generally require pretty flat terrain or ocean (not common in volcano territory) and a complex mix of warm and moist air, with cold and dry air coming from another direction. Again, this is not common in volcano territory like the Pacific Cascades, Kamchatka, or Japan. That said, however, it has been reported that tornadoes can pick up cars and carry them hundreds of meters away - even kilometers - and then drop them. Three tornado-hunter scientists from Denver were killed that way this last May (2013).

So. IF there was an erupting volcano, AND a tornado passed through nearby, it's conceivably possible that a tornado could pick up a bit of lava. However, lava is pretty dense. By comparison a car is much less dense (it has a lot of air space in it). More likely, the tornado would pick up ash and tephra (tephra is cooled lava filled with gas bubbles, so it is not very dense) and throw these around.

Something like this is not all that unreasonable, actually. There was a tropical cyclone (a Pacific hurricane) passing through the Philippines when Mount Pinatubo erupted in 1991. The effect of the hurricane-force wind, the HUGE amount of water that the cyclone brought with it, and the really huge volcanic eruption made quite a mess of the island of Luzon. It basically destroyed Clark airbase and badly damaged the nearby Subic Bay naval facility - and even though evacuations had been ordered, it still killed a lot of people.

~~~~~

Thorin later replied:

Thank you very much Jeff and it answers my question in great detail. Thank you for taking your time to answer my question and give me a very helpful answer.

~~~~~

What states are safe from earthquakes?

Where are you safe? Really nowhere. If you live in the Pacific Northwest, tornadoes are extremely rare, and hurricanes non-existent - but you are at risk of a large subduction earthquake and floods. If you live in the Southeast, you generally don't have to worry about earthquakes, but you are certainly living in Hurricane Alley. When I first took up my 5-year assignment to serve as chief scientist for volcano hazards in Vancouver, WA, in 2002, I was frequently asked the question: will we have a big eruption soon? I told everyone that I had voted with my feet, made an informed decision, and bought a house in Clark County. Two years later, of course, Mount St Helens erupted. While it briefly threatened the Johnston Ridge Observatory north of it, it was never really a threat to people in Clark County... though an ash-plume erupted on March 5, 2005 did apparently intersect an aircraft flight-path near Roseburg, WA. At least three Boeing 747 aircraft have lost all or almost all of their engines when they flew through a volcanic ash cloud. The aircraft flying over Roseburg was diverted to a nearby airport, thoroughly checked out, and found to be OK however.

Q: I saw on your website that 39 states are endanger of earthquakes, what 11 are not and why?

 Kaitlyn S, 8th grade Endeavor Charter School student

A: Hi, Kaitlyn,

If you go to this web-page you will see a map of earthquakes in the United States:

http://earthquake.usgs.gov/earthquakes/states/seismicity/:

You can count 11 states that have no recent seismicity (no red circles) - but this doesn't necessarily mean they are earthquake-free. 

The longer answer to your question is that earthquakes happen where there is crustal movement: mountains rising (Hawaii and Utah, for instance), crustal slabs sliding past each other (California), or continents riding over oceanic plates (most of the West Coast). If you look at this map, you will see states that have no apparent earthquakes. This is because they are in the center of a very old, stable continental crust, and not on the tectonically active margins. However the map of RECENT seismicity could fool you into thinking that Oregon is relatively free of risk. In fact, the same subduction fault off the coast from northern California to British Columbia threatens the western sides of three American states and one Canadian province. This kind of fault may not rupture for centuries at a time. However, when it does break it will be a real attention-getter. 

One thing to keep in mind is that distance from a fault offers increasing protection: Western Washington State is at much greater risk than eastern Washington State, for instance. This is because the energy of the earthquake falls off with distance, just like sound does. Sit on the edge of your bed and have your brother kick the edge next to you. If he then goes around and kicks the other side, it will not feel nearly as uncomfortable to you. 

~~~~~

 

Are tsunamis and volcanic eruptions a result of other catastrophic natural disasters?

Catastrophes are often related: a drought in southern California leads to wildfires, and within a year the denuded terrain is damaged further by floods and landslides because the vegetation that preserves and protects the ground surface is missing. A massive earthquake in Haiti leads to a devastating cholera epidemic, because people are displaced and water sources are compromised. The following query is from a thoughtful young man trying to understand some of these relationships.

Q: hello, my name is Brendan and i have a question related to geology in which i would like u to answer. so ya, here it is: Why do tsunamis and volcanic eruptions often act as a result of other catastrophic natural disasters? ya so please respond to this. Oh and btw I am a student at endeavor charter school, just to let you know. alright well thanks for your time and i hope to get a response. – Brendan J

A: Hi, Brendan - I can provide some brief answers.

Tsunamis are caused by SOME volcanic eruptions and by SOME earthquakes:

1. Thera volcano in the eastern Mediterranean erupted catastrophically around 1,500 BC. It triggered a tsunami that destroyed the Minoan civilization based on Crete. The 1883 eruption of Krakatau volcano in Indonesia sent a tsunami into the island of Java that scoured everything within 10 kilometers of the coastline and swept it all back to the sea. Contemporary descriptions said that you could walk across the Sunda Strait because of all the bodies (people, livestock) and logs floating there. MOST volcanic eruptions, however, do NOT cause tsunamis. For one thing, the volcano must be adjacent to an ocean for this to be possible. 

2. The tsunami that destroyed the Fukushima Di-Ichi nuclear powerplant, and destroyed much of the Sendai, Japan, coast, was caused by the Great Tohoku earthquake of 2011. The tsunami happened because a 200 km by 600 km slab of ocean floor was suddenly uplifted several meters by a sudden slip on a subduction fault offshore. The displaced seawater slopped onto the nearby coast, and a security camera showed a 15-meter (nearly 50 foot) wave crashing into the facility, wreaking nearly incomprehensible damage - that is still evolving as I write this. MOST earthquakes, however, do NOT cause tsunamis. There must be an uplift or down-drop of a large piece of ocean floor for this to happen.

Volcanoes are connected indirectly to subduction earthquakes - the Pacific Ring of Fire is an example of how they are related. A down-going section of oceanic crust, being over-ridden by a lighter-density continental crust (Sendai, Japan, and the coast of Washington State in the US, for instance), gives rise to volcanoes. The oceanic crust is heated up as it works its way deeper and deeper into the hot Mantle, and fluids in that down-going slab of oceanic crust contribute to partial melting. This is where lighter component elements of the oceanic floor float up until they burst through the overlying continental crust. Think of a lava lamp: it's the same general principle. Just offshore of North America, Kamchatka, Japan, the Philippines, and Indonesia (and many other places) there is a subduction fault where a continental section is riding over an oceanic crust. Just INLAND from these subduction faults you will find chains of volcanoes paralleling the same coastal margin - the Cascades Range extending from California to British Columbia is an example. One may not directly cause the other, but they are certainly related nevertheless. 

An earthquake was closely associated with to the 1980 eruption of Mount St Helens, but to this day geologists still argue about it. Did the earthquake trigger the eruption of the highly-unstable volcano? Or did the eruption cause the largest earthquake in recorded human history? 

~~~~~

Polluted wells

It’s hard to think of something closer to a personal threat than pollution in the water you drink. It’s also hard to comprehend that several billion people on this planet do not have safe water to drink. When a natural disaster hits, cholera frequently follows – because water sources are compromised. They can be compromised biologically or chemically. The following is an example query in this area of direct personal impact.

Q: Hi,

I'm trying to understand the concept and possible problems with groundwater and thought of a few questions,

So first, say there is a contamination in the groundwater and people notice it in their well, now what would a heavy spring rains do to this? Would it further contaminate it? 

What happens in case of drought, would you think the contamination would wear off?

Thanks.  - Banion

A: Good questions, and like all good questions, the answer(s) fall into an "it depends" range. That is to say, there are a lot of unknowns not clear from your question.

Let me try to answer via possible scenarios:

- A shallow well vs. deep well;

- Fracking may or may not be an issue;

- The pollutant was introduced externally, as opposed to via the well itself;

- The groundwater is recharged or not - a rainy vs. an arid environment;

- The pollutant is chemical (DNAPL/LNAPL/PAH), or it is Biologic.

Keep in mind that mitigation of a groundwater pollutant could fill at least a book by itself; with rare exceptions like some PAH's (Polycyclic Aromatic Hydrocarbons), water pollution rarely "wears off".

Here are just some possible scenarios with comments:

1. The well is shallow, and the pollution does not come from the well itself - in other words it was not introduced via the well:

    If you are just beginning to notice the pollution the odds are that a lead element of a pollution plume has just intersected the well. Continued drawing from the well will just pull more of the plume towards the well-head. In short: it will only get worse. The well may be lost, depending on the nature of the pollutant. If you can identify the source and it can be localized, there are steps you can take to isolate and mitigate the problem - but these steps are usually expensive and complicated.

2. The well is shallow, and the pollution was something inadvertently or deliberately dumped into it:

    Pumping will reduce the concentration gradually - but then you need to dispose of the polluted water that you draw up. If you simply dump it on the ground, it will eventually seep back to the water table, which in many environments is recharged from rain. The earth can function as as filter just so far.

3. The pollutant is biologic in nature (E. coli, for instance):

    Biological systems tend to equilibrate - and persist. If there is something like phosphates and nitrogen for the E. coli to feed on, it will grow. If no support is available (materials to feed on, warm temperatures to propagate in) then the biologics may go dormant - but they can be very long-lived as they wait around for a more favorable growth environment. If the biologic was introduced via the well itself, you would likely have to "shock" it with a chemical like chlorine (think of a complicated swimming pool), then pump until the well water passed a biological safety test - and treat the water that was pumped out, before it is disposed of. If the biologics arrive via the groundwater from a nearby feedlot, say, you may have to abandon the well. Industrial-scale pig farms are a true biological time-bomb.

4. The pollutant is a DNAPL, LNAPL, or PAH:

    A DNAPL (Dense Nonaqueous Phase Liquid) is one of a group of organic substances that are relatively insoluble in water - they will sink in water, are immiscible in but will not dissolve in water. An example would be a ruptured diesel fuel tank. A NAPL or LNAPL is similar, but not denser than water, and tend to remain shallow. These can all be really serious problems, though generally localized, and always very expensive to deal with.

    Instead of writing about this for a few days, let me instead point you at some useful links:

http://toxics.usgs.gov/definitions/dnapls.html

http://toxics.usgs.gov/definitions/napls.html

http://toxics.usgs.gov/definitions/lnapls.html

http://toxics.usgs.gov/definitions/pah.html

5. The pollutant is radioactive:

    Now we are talking about a Super Fund site, and the billions of dollars being poured into the World War II-era Hanford site in south-central Washington State is an example of this. During and following the World War, radioactive waste was buried in the ground in barrels, and dumped into single-walled tanks at Hanford and other sites around the country. This has happened all over the world. There is a vast region of the Caucasus in Russia and another near Chernobyl in the Ukraine that are both off-limits to human occupation, and the Great Tohoku tsunami of 2011 has made a significant area on the Sendai coast of Japan a dangerous wasteland. Plutonium may be the most toxic metal in the entire periodic table: micrograms can kill. At one point, plutonium was at detectable levels downstream from Hanford in the nearby Columbia River where I occasionally kayak.

6. Deep wells: 

    The water you are drawing is likely fossil - that is the recharge is slow at best, and that water has already been there for a long time (centuries or millennia). The groundwater may or may not be recharged. If you live in Saudi Arabia or Central Arizona, it's the latter case, and the well will eventually dry up. The ground itself will subside (damaging roads and buildings), and any pollution will likely stay with the water wherever it ends up. If you live in the Pacific Northwest of the USA, the groundwater is constantly being recharged via rain and snow. Any pollution will likely reach a steady state and then decline over time as it is diluted, but you may still have to abandon a polluted well. Most municipalities take extensive precautions to protect their reservoir watersheds for this reason.

7. Fracking:

    Fracking is hydraulic fracturing of "tight" geologic formations (like shale) to open them up and release trapped hydrocarbons. The process is technically complex, and involves injecting water and sand - as well as "proprietary" chemicals - at very high pressure into these tight formations. I might add here that if fracking is taking place anywhere near your water well, then your water is only protected as long as the fracking is deep, and the horizon being exploited is not connected to your groundwater - something that is nearly impossible to guarantee. It goes without saying that the fracking wells must be assiduously cemented and sealed - and subsequently monitored. We've all seen the videos of people turning on water in their kitchen sinks and literally igniting them with a match or lighter. 

~~~~~

 

I think I've found an impact crater

After "what is this rock", one of the most common queries we receive at Ask-a-Geologist is this: "I've found a circular structure on my property or on Google Earth. I think I've found an impact structure."

Q: Hello AAG,

I've been sitting in my room recovering from an accident so I've been "traveling the world" using Google Earth. But I believe I may have found an impact crater in New Mexico.

The coordinates are 35 53 52 N 104 53 22 W

If this is, in fact, confirmed to be an impact crater, I would love to name it 'Noble Crater' as this is becoming an increasingly rare trait in modern society and hope this discovery will IMPACT young, budding geologists in a positive way...pun intended.

Thanks!  - Dustin K

A: Hi, Dustin - hope you're getting better. 

You probably wouldn't be surprised to know you're not the first person to try doing this... or even the millionth. Gene Shoemaker, the "Father of Astrogeology", started an impact site search using air photos in the late 1950's, and started using LANDSAT when it became available in the early 1970's. When he died in 1996, he and his wife Carolyn had already spent many years trying to map all the impact sites in Australia, the best-exposed ancient continental craton on the planet - just to get a sense of how frequently the Earth gets whacked as a function of time. If you're being shot at, it helps your planning a bit if you know how often.

To the case at hand:

If you go to the geologic map of New Mexico (http://geology.about.com/library/bl/maps/n_statemap_NM.htm) ...you will see that your target area is in a large sedimentary province. A quick scan at the surrounding terrain shows that there has been significant tectonic activity (folding and uplifts, etc.) in this region. 

If you look at the Earth Impact database (http://www.passc.net/EarthImpactDatabase/NorthAmerica.html), you will see that there is just one confirmed impact site in New Mexico - the Santa Fe impact structure (6 - 13 km in size, over a billion years old, located at N 35° 45' W 105° 56'). 

The level of geologic mapping in New Mexico (and pretty much all of North America for that matter) is such that it's highly unlikely that an impact in New Mexico hasn't been previously discovered by the literally hundreds if not thousands of geologists who have been roaming it for the past century or so. That doesn't mean every impact has been found, nor does it mean that you haven't found something round. The problem is really two-fold:

1. There are a LOT more, simpler reasons for a round-ish geologic structure than an asteroid impact. These include tectonics, halokinesis (salt diapirs or domes), dissolution, magmatic intrusions, and even human involvement. Any circular structure in a sedimentary province is far more likely to be caused by any of these.

2. For this reason, it's really, really difficult to prove that a circular feature is an impact site to the satisfaction of other geologists. For starts, most of the known impact sites are ancient, and have been highly modified if not mostly erased by tectonics and erosion over time. We should look like the Moon, but we don't - and tectonics and our atmosphere are why. Only about 15 of the ~180 known impact features are "meteorite impact structures" - that means that parts of the original bolide are still present - the rest are just "impact structures". The ginormous Tunguska event in Siberia in 1908 flattened a forest the size of Rhode Island - but left no crater nor any measurable fragments. It was an atmospheric detonation. Thus it's typical for impacts to be lacking any obvious "smoking gun" evidence. 

Here is some helpful content for recognizing the subtle evidence of an impact feature: http://www.passc.net/EarthImpactDatabase/Criteria.html

There is more information, including some helpful images, in an article I wrote for Scientific American: http://volcanoes.usgs.gov/jwynn/1998SciAm-Wabar.pdf

From what I can see of your feature, it is an intersection of folds in sedimentary rock - but subsurface dissolution could also be involved. I have insufficient information about the local stratigraphy to say if this could be caused by halokinesis. 

My suggestion for YOU, however, is not to give up, but KEEP EXPLORING. You really deserve praise for not feeling sorry for yourself - but for instead trying to DO something. For this effort you get five stars ***** from a US Geological Survey scientist. Keep up that attitude. 

~~~~~ 

Best Place for a Geology Vacation? A World Tour.

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 "geology 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 crinoid - Mesozoic ocean 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 19^th 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 in Venezuela? 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.

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