More than 400 years ago, a massive meteor struck and buried itself in the sand dunes of the Empty Quarter of Saudi Arabia. We decided to make an expedition to the Wabar meteor crater in our Land Rover Defenders.

Not all sand dunes are created equal, especially when you travel in the dunes of the Empty Quarter. The Empty Quarter is a massive sandbox with more than a million square miles of sand.

In the northern Empty Quarter, sandy gravel plains gradually give way to small rolling dunes which eventually evolve into isolated crescent shaped barchan dunes.

Over time, these dunes coalesce and grow in height becoming progressively larger the farther south you travel.

On the southern reaches of the Empty Quarter you encounter massive mountains of sand.

A persistent high pressure area located over the Arabian Peninsula creates a clockwise flow of air associated with the high pressure area. Over many millennia, the clockwise winds pick up northern Arabian sand and distribute it in a giant swath over eastern Arabia finally depositing it in the dunes of the Empty Quarter.

The Empty Quarter becomes the final resting place of all the northern and eastern Arabian sands.

If you wanted to follow the trail of sand on its journey to the Empty Quarter, you would start in the Great Nafud of northern Arabia and travel for 2000 sandy kilometers through the sands of the Dhana Desert right down into the Empty Quarter. That would be ultimate sand trip in Arabia and worthy of any expedition.

This article isn't about the ultimate sand trip, but it is about driving in sand for nearly eight hundred kilometers in the Empty Quarter with a specific destination in mind. We are driving to Wabar close to the center of the Empty Quarter to examine a site where a large meteor augured into the Arabian Sands.

At Wabar, an iron meteorite traveling in excess of 25,000 kilometers per hour broke into four fragments and plowed into the Arabian sands with an impact rated as a 13 kiloton explosion similar in energy to the nuclear weapon that destroyed Hiroshima in world war II. Nobody knows for sure when the meteor strike occurred, but estimates place it about 400 years ago. The largest known chunk of the iron/nickel meteorite is on display at King Saud University in Riyadh. This chunk weighs in at nearly two and a half tons.

Our expedition will drive through the Arabian sands using three vehicles giving us good redundancy just in case a vehicle breaks down in deep desert. It's highly unlikely that three vehicles would have mechanical failures on such a trip.

I have driven to the Wabar Crater three times by three different routes. The difficulty of the trip is directly related to the selected route and the season of the year. If you go in rainy season just after the rains, the trip is much easier. If you travel in June, July, or August when the desert sands have zero moisture, you are asking for an extremely difficult and arduous trip, and if you make a serious mistake, you can be dead in a few hours in the 140 degree F heat. If you travel in a shoulder season with more temperate weather, you should be fine as long as your vehicles are well equipped for deep desert exploration and survival.

We always traveled in a Defender 110 when journeying in the Empty Quarter. During my sixteen years in Arabia, I owned three Arabian different Defenders, and all of them did deep desert exploration.

Green Defender cruises the desert sands on Michelin XS sand tires at about 18 psi inflation. Examination of the pictures show the ballooning of the tires giving excellent floatation in a loaded vehicle heading out for a week in the sand dunes. When I first started driving in sand, I tried driving at 25 psi, and I frequently bogged down and had to recover the vehicle with sand ladders, winch, or tow strap. Once I dropped the tire pressure down to 16-18 psi, I rarely got stuck. At those tire pressures I have never broken the bead and slipped a tire on the rim. I don't use any bead lockers.

We carry Arb air compressors to reinflate the tires up to 35 psi when returning to the asphalt.

Green Defender has an awning on the right side of the vehicle, and a tent mounted on the left side. The full length roof rack carries fuel, food, firewood, sand ladders, and assorted camping gear.

This is my third Defender 110 with a 3.9 liter V8 gas engine. This sand machine will take you anywhere you want to go in the Empty Quarter as long as you have enough fuel. The V8 engine is amazing. As long as you are in gear and have the engine under load, you can push the accelerator all the way to the floor in first or second gear without worrying about blowing the engine. It's not very fuel efficient, but you can nearly always blast through soft patches of sand if you are in the correct gear, and you have the accelerator all the way to the floor. I have never heard of anyone blowing their engines while working at maximum RPMs in the dunes.

This is the roof of Green Defender. The Brownchurch style roof rack carries eight jerry cans of fuel with jumper bars holding the jerry cans in place. The back of the roof rack has a mount for sand ladders and a high lift jack. The roof rack also carries boxes of water, boxes of firewood and a second spare tire.

On the left side of the roof rack is an awning with poles, and on the right side is a tent mounted to the vehicle.

On deep desert expeditions, we carry 13 jerry cans of fuel. Eight of the jerry cans lay flat on the roof rack, and five reside in a purpose made box in the back of the vehicle. In addition, we have an auxiliary long range tank in the right rear wing that empties directly into the main 80 liter tank. When fully fueled, we carry 430 liters of fuel for deep desert exploration.

We calculate fuel requirements in the following manner. Using a map measuring device, we trace our route on the map so that we accurately know the number of kilometers involved. From experience, we know that our Defenders get about 3.5 kilometers per liter on average in the sand. We divide the measured distance for the expedition by 3.5 to figure the amount of fuel needed, and then we add another 30 percent to compensate for all the zig zagging in the dunes. Using this technique, we usually come out of the desert with one jerry can still containing fuel at the end of the trip. We have never run out of fuel on a deep desert expedition.

This trip has three vehicles. Two Defender 110s, and one Toyota Land Cruiser. The Land Cruiser is running a 4.5 liter engine, and the two Defenders have 3.9 liter V8s. All the vehicles have plenty of power to deal with heavy loads and soft sand. The White Defender and Land Cruiser have one advantage over the Green Defender. Both have Shaheen sand tires designed for conditions just like this. Shaheen sand tires have excellent flotation, and sometimes they float over the dunes while my Michelin XS tires sink into soft sand.

When I first started driving in sand, I thought that wider tires might be better in the dunes. It turned out that wider street tires did not work better. They tended to act more like a sand plow and provided less flotation. In really soft sand, they pushed sand in front of the tire piling it up especially at slower speeds.

Shaheen sand tires have zero tread. They are like aircraft tires, and they tend to hydroplane on wet streets. You must be very careful driving on Shaheen tires on asphalt after a rain shower. You may slide around like you are driving on ice.

People who spend lots of time in the sand frequently have two sets of tires for their Defenders. One set is for driving on the streets around town. The second set goes on just before you go on a trip in the dunes.

Our first camp on this expedition is in the small dunes of the northern Empty Quarter. In this area, the dunes are like small rolling hills of sand. You drive up one side of the dune and down the other side without encountering a slip face. The dunes are tall enough that you cannot see what's on the other side, but you can drive on them at a good speed because you know there isn't a slip face on the other side.

The terrain is flat sandy plain with rolling hills of sand. When it's time to camp at night, you pick a flat location that has firm ground so that your Defender doesn't bog down at your chosen campsite.

Camping in the dunes is generally safe as long as you observe a few important points.

Don't camp too close to the last sand dune that you crossed before you set up camp. The reason is straightforward. When Bedouins drive in the desert, they often follow the tracks of vehicles that are ahead of them. This makes it much easier to read the sand, If the tracks are solid, and if they don't sink into the sand, then route finding in the dunes is much easier. You find a set of tracks heading toward your destination, and you follow them. If the tracks show that the leading vehicle bogged down, the following vehicles diverge off the track so they also don't get stuck. If the track looks good, they continue driving with much greater freedom and speed.

Bedouins often drive in the desert at night when it's cooler. If they like your track and follow it, you may have a rude awakening in the middle of the night when they pop over the dune and into your camp. Most likely it will scare both them and you. No harm is done as long as you are not parked immediately on the far side of the dune.

On this particular campsite, that is exactly what happened. My daughter wanted to camp at the base of the dune in the direction from which we just came. She wanted to tuck her sleeping bag in the danger zone. I told her that it was too dangerous, and she relented. In the middle of the night, a truck came over the dunes and would have run over her if she has been in that location.

We parked the Defender so that it protected everyone sleeping in our two tents. That way if someone came barreling though at night, they might hit our Defender, but they would not run over us as we slept. I probably should have had put my Defender farther away from the dune to reduce the risk to the Defender.

The other two vehicles camped further out on the sandy plain, and there was no danger of being run down in the night by anyone unless they were intoxicated or blind. Examination of the white shelter between the two vehicles shows that the wind is blowing hard in this section of the northern Empty Quarter.

After traveling 200 kilometers south, the sandy plains and rolling dunes disappear. Barchan dunes surround us on all sides, and as we journey south, we slide down hundreds of slip faces as we traverse row after row of dunes.

Because the prevailing winds are out of the north, the barchan dune lines are oriented east to west. A single row of dunes can extend for hundreds of kilometers in the southern Empty Quarter.

Once the Barchan dunes begin in earnest, you cannot drive around them. It's over the top and down the slip face as you head to the center of the Empty Quarter. Heading south is the easy direction of travel. When you turn around and go back the other way, you spend lots of fuel and time searching for sand ramps that will allow you to ascend the dunes to get around all the slip faces that dominate the countryside.

When wind blows strong out of the north, the sand flies in sheets off the tops of the dunes. If you get downwind of these dunes, you better put on your sand goggles, or you will get a ton of sand in your eyes.

The blowing sand deposited on the downwind side of the dunes takes a long time to compact into firm sand. It frequently is powder soft, and if you attempt to drive there, you may sink up to your chassis. You wouldn't want to drive or camp there because blowing sand gets into everything and camping is miserable.

Sometimes you get stuck at the bottom of a slip face because you are going too slow as you descend, and when you hit the bottom, a soft sand trap awaits. This tends to be a greater problem in larger dunes than smaller ones. As you come slowly down the side of a slip face, it's a good idea to accelerate near to the bottom just in case you are entering a sea of soft sand. A heavy foot on the accelerator may allow you to power through the sand trap and move forward far enough to get on firm ground.

Bushes and obstacles on the far side of a slip face can be a nasty surprise. You pop over the top of the dune, and foliage at the bottom blocks your way at the base of the dune. That is a great formula for getting stuck at the bottom, and it will be a major exercise in vehicle recovery because maneuvering options are limited.

Calculating your fuel requirements must take into consideration that traveling in the dunes is a two way street. You probably are going to return home in approximately the same direction from which you came. Going against the dunes requires more fuel than going with the dunes.

When you go south with the dunes all you need to do is ride down the slip faces and enjoy the trip.

There will be soft patches here and there that will stop you in your tracks for a short time, but at least you are not traveling against slip faces.

Going against the dunes requires more fuel and route finding is a bigger challenge. You can't travel in a straight line. You spend time traveling in the valleys between the dunes looking for sand ramps that will get you over the slip faces. Sometimes, you may need to drive ten kilometers before you can find a sand ramp that will get you over a particularly large dune with a giant slip face.

The left side of this picture has several sand ramps that are good candidates for getting you up and over the dune line.

Going against the dunes gets more complicated when dunes are stacked on one other in two or three levels. In this situation, you find a sand ramp that gets you over the first row of dunes, and then you drive on the higher level looking for a second sand ramp that will put you over the second row.

Sometimes there is no way over the second or third level, and you have to descend back down from whence you came. Then you travel parallel to the dunes once again until you find another sand ramp and attempt to go up and over, and hopefully around the slip faces that block your way home.

Reading the sand is difficult. The lead vehicle that does route finding is the one that gets stuck most frequently. It's simply a fact of life when you drive in sand. There is simply no way of knowing that sand will be soft by just looking at it.

If it is important that we don't get stuck for some strategic reason, then the best way to find out if the sand is soft is to get out of the truck and walk in front of the vehicle. You walk to the right, left, and straight ahead.

If you are lucky, firm sand may be two feet in front of your truck. Sometimes, if you turn left you will be on terra firma in ten feet. But when you walk in front of your truck, and there is nothing but soft sand for hundreds of feet, the smart thing to do is to come out backwards. It's faster and less exhausting on people doing vehicle recovery.

If the ambient temperature is 100 degrees, it's not safe to use sand ladders and push by hand when vehicle recovery requires an hour of hard work. Someone will get heatstroke at worst, and everyone will end up dehydrated at best.

The Land Cruiser determined that it was impossible to move forward to firm ground, and the quickest and easiest way to recover this vehicle is to use a winch. In a few minutes of winching, the expedition is once again on the way to the meteor crater.

Later in the day, shadows grow longer and sand takes on a darker appearance. Depending where you are in the Empty Quarter, sand varies from a reddish color to a pale tan, and everything in between.

Getting between the slip faces in this picture would be easy as there is a well-developed sand ramp between the two slip faces. It doesn't get any better than that when you want to travel against the dunes.

As you travel south, rows of dunes often spread out. You may have two or three closely spaced rows, and then you have rolling hills of beautiful sand for a kilometer or more before you come to the next row of well-developed dunes. In the valleys between the dunes, the sand tends to be firm, and it's pure joy to glide over the sand. The tire tracks to the right show that the sand is relatively firm. When I drive over sand like this it reminds me of sailing over ocean swells in the Pacific Ocean, and the best thing is that the sand swells don't move.

It's late afternoon, and shadows grow long as the golden hour approaches. Sand takes on a golden hue, and life is good. Tire tracks in the foreground reveal the presence of exceptionally firm sand.

Why does this campsite have a circle of tire tracks all around?

We commonly make such a circle when choosing our camp just to be certain that we aren't setting up a camp in soft sand. If we bog down when we drive in a circle, we move to a different location.

Ending the day by bogging a vehicle in a campsite is a poor way to finish an expedition in the dunes. Equally, waiting until morning to extract a bogged vehicle is not the best way to start a day.

Hence, we drive around our campsite to test the sand before we choose our final resting place for the night.

Reading the sand is most difficult at high noon. Shadows from the morning are gone, and intense sunlight directly overhead reduces contrast to such a low level that it's easy to make serious mistakes. Without the contrast, you may drive off a small slip face without realizing it's there until your car suddenly drops three feet - a very rude awakening. The opposite can occur. You may not see a two foot sand ridge in front of you until your vehicle hits it and pops violently up over the elevated sand ridge. Mistakes like that place great strains on your suspension and frazzle your nerves. One of my friends drove his Defender off a small slip face that he did not see, and flexing of the vehicle's chassis resulted in a permanent wrinkle in the skin of his Defender next to his left rear tail light. Hogging of the frame can put creases in the sheet metal.

I have seen Defenders pop over a ridge of sand that they did not see, and suddenly the vehicle starts making a horrible grinding noise. When the Defender went over the sand bump too fast, it broke one of the engine mounts. Now when they step on their accelerator, the engine twists slightly in the engine bay, and the fan rubs on the fan shroud making a horrible noise.

When I was learning to drive in sand, my instructor showed me how to bump my Defender over a three to four foot slip face (from the wrong side of the slip face). If you drive up to it at just the right speed, your Defender will bounce up and over the slip face. It's a great technique when it works, but it's also the recipe for breaking an engine mount. If you are going to do stuff like that, you better carry spare engine mounts when you are traveling in deep desert.

Although there isn't much contrast in these dunes, you have one important factor in your favor. Wheel tracks ahead of you reveal a safe path through the dunes. By looking at the tire tracks, you can see where the sand is firm and where it is soft, so you know when you need to step on the accelerator. When the going gets tough, and there is no contrast in the sand, we always look for tire tracks to make our journey easier.

In the foreground just beyond the ripples in the sand, a light colored band goes from one edge of the picture to the other. This light golden band is one of those tricky sand surfaces that can fool you as you approach it in conditions of low contrast. The golden band may be a three foot high wall of sand that you may pop over and in the process break an engine mount. That same surface may have a gentle slope and not be a problem. Sometimes you have to stop your truck a distance off to discover what's happening so you don't make a serious mistake in deep desert.

This line of closely spaced dunes is very tough to navigate at high noon.

You don't want to drive fast because low contrast makes it easy to to have a problem. At the same time, the dunes are closely spaced with an irregular pattern of sand hills.

In this location, winds alternate between two different directions.

The dominant wind pattern is from the north causing the longitudinal rows of dunes. But in between the longitudinal dunes are secondary dunes created by winds from the east.

The jumble of east/west dunes mixed in with north/south dunes means tough going, especially at high noon when there is little contrast.

I would avoid the dunes in the distance and make my best efforts to escape this mess by traveling right to left in the foreground where there are some barely perceptible tire tracks on the left side of the picture.

Low contrast means drive with care. Whether you are heading north or south, it appears that these two lines of dunes terminate about a kilometer in the distance. In this case the better part of valor is to make an end run around the dunes rather than try to go over them in conditions of low contrast.

Contrast is relative low, but a passage through the dunes looks within the realm of possibility. The dunes are closely spaced, and if the sand is soft, you are in trouble. Trucks will bog down. If the sand between the dunes is firm, you will breeze though wondering what everyone was worried about.

Driving down a slip face is true joy. The sand on this slip face is relatively firm as the Defender isn't sinking down to the chassis as frequently happens on large slip faces.

Red Land Cruiser is gutting it out driving through soft sand on Shaheen sand tires.

I have seen him drive out of a bogging situation like this by lowering tire pressure down to 8 psi, and then putting the vehicle in lowest gear and slowly creeping forward or back.

You can quickly tell whether you can creep out of a sand bogging by watching the vehicle and tires. If the vehicle moves forward or back a tiny bit at a time, the technique may work. If the tires simply spin and the vehicle sinks down further, then it's useless to continue spinning the tires. It will only make things worse.

If you have sand tires and you are willing to lower your pressure down to 8 psi, you can sometimes drive out of a serious bogging.

When I first drove in the Empty Quarter, I coined a new saying, "SASTRUGI HAPPENS".

Sastrugi are the wavy elevated ridges of sand created by blowing sand.

Sastrugi comes in two types. There is hard sastrugi and soft sastrugi.

Sastrugi happens in the valleys between the dunes. Hard sastrugi is very hard, and feels like driving over giant corrugations or speed bumps. It will shake your vehicle until you wonder if something is going to break. It will shake your teeth until they rattle.

Soft sastrugi is soft like quicksand. It looks like you are going to be hammered by severe corrugations as you approach a patch of sastrugi, but the instant you enter it, you immediately sink up to your chassis in soft sand.

You can't tell ahead of time whether the sastrugi is going to be of the hard or soft variety. You simply must drive though it to find out what is going to happen.

If you think the sastrugi is soft, you step on the gas and try to blast through it. If it turns out that the sastrugi was actually hard and you are going too fast, the sastrugi will shake your vehicle to bits, and unsecured gear will be flying around in your truck by the time you reach the other side.

If you think the sastrugi is hard, you let up on the accelerator and slow down so it won't shake everything up. If it turns out that the sastrugi is actually soft, you instantly bog down in the soft sand. Some days you feel like you can't win.

When you encounter sastrugi, you have several options. You can drive around it like a skier doing the giant slalom. You can stop your truck before you get to the sastrugi and walk through it to see whether it is hard or soft. You can hang back and let someone else drive though it. You instantly discover whether it is hard or soft when you look at his tire tracks. If it is soft, you put your foot down and blast through. If it is hard sastrugi, you drive though at a slow and gentle pace.

In late afternoon, the dunes look like King Midas reached down and turned the dunes to pure gold. This is the stuff from which sand dreams are made. Every time I set up my camp in the golden dunes, I feel like I won the lottery of life, and this is my prize. I could come back to these dunes a thousand times and never tire of them.

We like to arrive at camp by 4 p.m. so there's plenty of daylight to set up camp and cook our supper before dark. In the late afternoon, we have a chat about possible places to set up our tents. It's not hard to find a place in a million square miles of sand. The only decision is whether you want to camp high or camp low.

The people on this expedition generally prefer to camp high so they have a tent with a view. Other's prefer to camp low where it's harder to be discovered by passing vehicles.

During daylight hours, you are never aware of other vehicles in the Empty Quarter. But at night the desert comes alive. You sit around the campfire or lie on your cot listening to vehicles far off in the distance. If you pop your head out of the tent, you see the loom of headlights bobbing in the night sky as Bedouins drive at night in the dunes.

In the daytime far off the beaten path, you feel like you are exploring an isolated solitary world. At night you realize you are never alone.

I wonder where we should go next? Hmm. I know. We'll just follow these tire tracks and discover the Wabar meteor crater in the center of the Empty Quarter.

Welcome to the Wabar Meteor Crater, also known as Hadida.

The Wabar meteor broke up into multiple fragments before it struck the dunes. It's unclear how many craters are present at Wabar, and we will probably never know. That type of research takes lots of money to answer questions that only a few people are asking. Some craters are obvious, and others have filled in with sand in the past four hundred years. Lots of sand gets moved around in the Empty Quarter in 400 years.

When the meteor struck the dunes, it ejected tons of superheated debris in concentric rings around the impact site. It looks like the remnants of a giant campfire in which the sand caught fire leaving charred remains.

Donna stands on the sloping side of a meteor impact site. At the present time the hole is no more than 50 feet deep compared to the present height of surrounding dunes. One wall of the impact site is relatively vertical, and the other side slopes gently downward and is covered with melted and compressed sand.

The color of the debris varies significantly from location to location. Some areas have mostly white debris, and in other areas the debris is mostly black.

This debris ejected from the impact site gives a clue to the location of the meteor strike. Since the force of the meteor hitting the earth was the equivalent to that of a thirteen kiloton bomb, it surely must have created a deep hole. One the other hand, scientists believe the meteor came in at a very low angle, and that may limit the size and depth of the original crater. According to excavations in 1932, the largest crater was12 meters deep.

Debris consists of white impactite (a sandstone like rock formed from compressed heated sand), and black glass formed from melted sand. The impactite appears white through and through, and you can see the striations where layers of sand were compacted together. The black glass rock was molten, and it takes different forms. I contains bits of impactite, and fragments of the iron and nickel meteor.

The laminated compressed structure of white impactite is clear. It is lightweight and feels like piece of white cinder.

Melted superheated sand formed the black glass seen all over the site. Some of the smaller pieces of black glass look like black tear drops. Some have an obsidian-like appearance but without conchoidal fractures seen in obsidian. Melted black sand incorporates white pieces of impactite and rusty meteor fragments. This specimen of black glass has two spots of rust from the iron found in the meteorite.

The Wabar meteor is composed of iron and nickel. The alternate name for this site is Hadida which is the Arabic word for iron. Even before geologists understood the nature of this site, Bedouins had figured out that it was a source of iron in the middle of the desert sands. Hence, they named it Hadida.

Extensive fields of impactite and black glass surround the Wabar crater.

Sand dunes are gradually reclaiming the impact site. Wynn and Shoemaker's article in 1998 Scientific American magazine states that the largest crater was 12 meters deep in 1932, eight meters deep in 1961, and nearly filled with sand by 1982. It won't be long in the geologic time scale before Hadida disappears below the sands. If you want to know more about the Wabar Crater and its geology, search Google for "The Day the Sands Caught Fire" by Wynn and Shoemaker.

As the winds from the north deposit more sand in the Empty Quarter, the Wabar Crater will eventually disappear beneath the dunes. The craters will fill in and the impactite and black glass will be covered by advancing dunes.

The big hole at Hadida is nice to look at, but don't ever drive your Defender down into the hole. It will stay there forever because there is no way to drive out.

Holes like this are a reminder to pay attention to what you are doing in the dunes.

Always look before you leap, because some mistakes are forever.

The further south you head in the Empty Quarter, the bigger the dunes become.

I have driven down slip faces that are more than 200 feet high, and before you drive down, you better be 100 percent sure that you are not descending into the pit of despair. It's hard to imagine anything worse that leaving your Defender in the Empty Quarter because you stupidly drove it into a hole.

On the trip back from Hadida, I had my opportunity to lead the expedition into a sea of soft sand. It was high noon, and I had no clue that in a few seconds I would be up to my chassis in golden sand.

If I had a thousand dollars for every time I have been stuck, I would be a millionaire.

I'm grateful for all the times I've been stuck over the years. That's what happens when I live my dreams.

I've been up to my axles in sand hundreds of times. That's terrific because it means I am living my sand dreams.

I've been stuck too many times to count, and I hope my good fortune continues.

Life is good.

Dr. Dave

Save A Tree Bookstore

Although I like the feel of a paper book in my hand, I love trees even more. When people purchase an eBook, they actually save trees and save money as well. Ebooks are less expensive and have no negative impact on the environment. All of Dr. Dave's books are available at Save A Tree Bookstore. Visit the bookstore today and start putting good things into your mind. It's easy to fill your mind with positive things using eBooks. No matter where you are or what you are doing, you can pull out your smart phone or tablet and start reading. You can even use electronic highlighters and make annotations in your eBooks just like paper books.