What is the Marcus Landslide Trail?
Here is a sentence that should be better known in Scottsdale: a mountain fell down at the edge of town, and nobody noticed until 2002.
The Marcus Landslide Trail runs east from the Tom’s Thumb Trailhead — about 1.5 miles each way, wide and smooth and almost flat, with an optional 0.7-mile loop that climbs up onto the wreckage itself. What you are walking toward is the collapsed face of East End, the highest summit in the McDowell Mountains. Roughly 500,000 years ago a slab of that mountain let go and ran about a mile out onto the desert floor. Researchers put the moving mass at something on the order of 26 billion pounds of rock and soil, spread into a lumpy debris field roughly 4,000 feet long and 1,650 feet wide, standing more than 100 feet above the original ground surface. Look back at the ridge and the breakaway scar is right there, unmistakable once someone points it out.
Somebody did point it out, relatively recently. The slide was recognized in 2002 by ASU graduate students John Douglass and Brian Gootee on a field trip, and named for the late Melvin Marcus, an ASU geography professor and alpinist. It is understood to be the second-largest known landslide in Arizona — the Grand Canyon holds the record.
The trail that resulted is the Preserve’s best piece of teaching. It is signed at intervals with explanations of erosion, granite weathering, lichen, and the Pleistocene animals that once walked here, and the signs are genuinely good: the kind that change what you are looking at rather than just naming it. It is also, by a wide margin, the easiest serious hike leaving the Tom’s Thumb lot.
How to hike the landslide right
Turn left, not right. At the trailhead everything funnels uphill toward the spire. The Marcus Landslide Trail heads the other way, and the difference in traffic is immediate. You get eastward views toward Four Peaks and the Mazatzals, a wide groomed tread, and a fraction of the crowd.
Understand the grade before you commit. The outbound leg trends gently downhill, which feels wonderful and means the return is gently uphill for a mile and a half. That is nothing in January and it matters in May. Do the walking early.
Do the loop. Plenty of people reach the base of the debris field, read a sign, and turn around. That is the wrong call. The 0.7-mile loop climbs into the boulder jumble — a chaos of house-sized blocks, mushroom-shaped weathered granite and ground that makes no geological sense until you know what happened. Two hundred feet of climbing, maybe, and it is the entire point of the trip.
Bring all your water. The Tom’s Thumb Trailhead has restrooms and shade ramadas but no drinking water. For three to four flat miles in cool weather a liter each is plenty; in warm weather this stops being an easy trail and starts being an exposed one.
Parking is the Tom’s Thumb problem, inherited. From December through March the lot fills by 7:30 on weekends, even though most of those cars are going up, not east. Arrive by 7 or roll in around 2 p.m.
Go with a steward if you can. The McDowell Sonoran Conservancy runs free guided hikes out here, including geology walks, and this is the trail where a guide pays for itself — a landslide is the sort of thing that is invisible until someone shows you the scar, the hummocks and the run-out in one sentence.
Pair it well. Fit hikers stack it with Tom’s Thumb from the same lot. Everyone else should pair it with the flat, saguaro-dense trails at Brown’s Ranch or the accessible nature path at Gateway Trailhead for a full desert day without a single grim switchback. Background reading: our guide to the McDowell Sonoran Preserve as a whole.
How a mountain collapsed at the edge of Phoenix and nobody noticed
The McDowell Mountains are old, hard, and mostly granite, which is a combination that suggests permanence. They are not permanent. Half a million years ago, give or take, the northeast face of East End — the range’s highest summit, standing above what is now the Tom’s Thumb Trailhead — failed catastrophically.
The numbers researchers have reconstructed are difficult to hold in your head. Something on the order of five and a half million cubic meters of rock, weathered granite, soil and vegetation came off the mountain at once: about 26 billion pounds of material, reaching speeds estimated near 44 miles per hour, traveling roughly a mile before it stopped. What it left is a slide mass about 4,000 feet long and 1,650 feet wide, piled more than 100 feet above the desert surface it landed on, and a raw breakaway scar still legible on the ridgeline above.
And then, for hundreds of thousands of years, the desert did what deserts do. Saguaros colonized the rubble. Palo verde and creosote filled the hollows. The sharp edges rounded into the mushroom-shaped weathered forms the trail now passes. The result looked, to almost everyone who ever walked across it, like ordinary lumpy McDowell foothills — boulder-strewn bajada, of which greater Phoenix has thousands of acres.
The recognition came in 2002, and it came from students. John Douglass, then a doctoral candidate in geography at Arizona State University, and Brian Gootee, then a graduate student in geology, were on a university field trip in the McDowells when the topography stopped adding up: the hummocks, the scattered oversized blocks, the scar, the run-out all pointed one direction. They had found what would be described as the second-largest known landslide in Arizona, a couple of miles from a trailhead, on the urban fringe of the sixth-largest metropolitan area in the United States. Mapping and published work followed, including a formal description of the feature as a large landslide at the edge of metropolitan Phoenix.
The name honors Melvin Marcus, an ASU geography professor, mountaineer and — by every account written about him — a serious mentor of field scientists. Naming a landslide after a teacher is a decent joke and a real tribute at the same time.
What turned the discovery into a public amenity was the city’s timing. The northern McDowell bajada had been coming into Preserve ownership since the 1995 tax vote and the 2004 expansion, and when Scottsdale built the permanent Tom’s Thumb Trailhead in 2012, the landslide sat an easy mile and a half from the new parking lot. The trail was signed and interpreted, the Conservancy’s stewards started running geology hikes on it, and a feature that had been invisible for half a million years became something a family with a stroller-aged kid could go look at on a Saturday.
Why it matters
Most interpretive trails are decoration — a plaque naming the cactus you were already looking at. This one does something harder: it hands you a piece of evidence and teaches you to read it, and the thing you learn is that the mountains on Scottsdale’s eastern skyline are not fixed scenery but geology in progress, capable of dropping a chunk of themselves onto the desert at forty miles an hour. That the whole story was only recognized in 2002, by graduate students, within sight of the city, is the best possible argument for the Preserve’s existence. Land you have not built on is land that can still be studied. Thirty thousand acres of it, and we are plainly still finding things out.