I am very excited about this hike. I am a geologist and this is a hike to Marcus Landslide by one of the guys who discovered it. This landslide happened thousands of years ago (no exact date) when Phoenix was a wet environment, but was only discovered fairly recently. This educational hike will be led by Brian Gootee (the geologist) and may be up to 3 hours long. This hike is suitable for just about any hiker (new and old).
If you have never been to the Tom's Thumb trailhead go to http://mcdowellsonoran.org/event/displayEvent/295#sthash.EnQSGBVp.NmENLUpd.dpbs and click on "Tom's Thumb" in the location line. Don't rely on your GPS telling you how long it takes to get there and the road to the trailhead is new so your GPS may not know that road exists.
Please arrive no later than 7:45 and try to get there for 7:30. No dogs are permitted on guided hikes at the McDowell Mountain Conservancy. Bring at least 1 liter of water, I suggest 1.5. The Conservancy will have you sign a waver to attend their hike as well so keep that in mind.