 | The hiking group totaled five on Day 3 of the Geotrek. Pictured here along the side of Mulholland Drive at the head of Encino Hills Drive, from left to right, are Gene Fritsche, Sue Fritsche, Judy Maller, Esther Meyers, and John Alderson.
 | Visibility on Day 3 was superior to what it had been on the first two days. Here's a nice view of the Encino Reservoir from Mulholland Drive with the San Fernando Valley, the Simi Hills, and the Santa Susana Mountains in the background.
 | At this point the intrepid group has left Mulholland Drive and is hiking along the Eagle Rock Fire Road at the junction with the Cheney Fire Road. The San Fernando Valley and the San Gabriel Mountains are in the background.
 | Here we are at Eagle Rock, sitting on the southern wing. Note the cave in the lower left corner of the photo and go to the next picture for a look inside.
 | Inside the cave under the southern wing of the eagle at Eagle Rock are these paintings. If you believed they were prehistoric in origin, I'm sure you could come up with all sorts of native stories regarding what they were depicting.
 | Day 3 was a pretty hot day - a high temperature of 93°F was recorded in nearby Woodland Hills - but we made it to the end of the hike at the Dead Horse parking area in good spirits.
 | The oldest rock formation in the Santa Monica Mountains is exposed in the roadcuts along Mulholland Drive for the first 2 miles of this leg of the hike. The rock unit is referred to as the Santa Monica Formation and it is composed of a dark gray, mildly metamorphosed slate. A few fossils still preserved in the slate establish the age as Late Jurassic, about 150,000,000 years old.
 | Intruded into the Santa Monica Formation slate is the quartz diorite that was seen on Days 1 and 2. This photo is a closeup of what the quartz diorite looks like in this area.
 | This is a spectacular exposure that can be seen along the Farmer Ridge trail about 2.5 miles from the start of the Day 3 hike. Here the dark gray slate in the left and upper center parts of the photo has been intruded by a very light gray, intrusive igneous granodiorite. Based on the age of the granodiorite in Griffith Park, this event occurred about 100,000,000 years ago and very deep within the crust of the Earth. Overlying the slate and the granodiorite at the top of the photo is a brown conglomerate and sandstone rock unit called the Monterey Formation. It is about 12,000,000 years old. In order for these relationships to exist, the slate and granodiorite had to be uplifted and very deeply eroded before the conglomerate and sandstone were deposited on top of them. Note the light-colored boulders of granodiorite in the conglomerate that prove that the granodiorite was eroding and being incorporated into the conglomerate.
 | Deposited on top of the Santa Monica Formation east of the junction of Mulholland Drive with the Bent Arrow trail is the red-brown boulder conglomerate shown in this photo. It is called the Trabuco Formation and was deposited in alluvial fans that entered a river valley about 90,000,000 years ago during the Late Cretaceous period.
 | Along the Bent Arrow trail and Fire Road 30 are exposed conglomerate and sandstone beds of the Tuna Canyon Formation. They were deposited on top of the Trabuco Formation in shallow-marine environments during the Late Cretaceous period between 90,000,000 and 75,000,000 years ago.
 | This photo shows some of the sandstone beds in the Tuna Canyon Formation. John showed us that within some thin limestone beds in this formation are fossils of the ammonoid genus Scaphites. The ammonoids we found were about one-quarter inch in diameter and prove that the formation was deposited in the ocean.
 | Just north of Hub Junction on Fire Road 30 is this exposure of the Santa Susana Formation that was deposited on top of the Tuna Canyon Formation. The rock is mostly a greenish-brown siltstone like is shown in the bottom part of the photo, but the formation also contains lenses of white limestone like the one in the top-center. The limestone is composed of the skeletons of calcareous algae, plants that can live only in marine water that is shallow enough for sunlight to penetrate. Other fossils in these rocks show that they were deposited during the late Paleocene epoch about 55,000,000 years ago.
 | This photo shows a bold exposure of a reddish sandstone and conglomerate unit that occurs just south of Hub Junction. It is called the Sespe Formation and was deposited on top of the Santa Susana Formation in a river environment that existed here about 40,000,000 years ago. The resistant red sandstone is truncated on its left end by the Santa Ynez Canyon fault.
 | Shown here is a closeup of a conglomerate bed in the Sespe Formation. It was deposited along the bottom of a river channel. Note that the Sespe and Trabuco (see photo 10 above) Formations are similar in color and texture because they were deposited in similar sedimentary environments.
 | Eagle Rock doesn't look like an eagle when viewed from the south. Eagle Rock is a resistant exposure of the Lower Topanga Formation that was deposited on top of the Sespe Formation about 25,000,000 years ago. The formation here consists of shallow-marine sandstone and conglomerate and much more of it will be seen on the following hiking days.
 | Along the Eagle Springs Fire Road, the Sespe and Lower Topanga Formations have been intruded by a dark gray igneous rock called diabase. Shown here is a closeup of the diabase that was intruded about 17,000,000 years ago.
 | Pictured here is a phenomenon referred to as spheroidal weathering. It is common in this area within the diabase intrusive rocks. Cracks in the diabase break up the rock into adjoining blocks. Water seeping along the cracks weathers (decomposes) each isolated block from the outside in toward the center. The weathered rock peels off the unweathered core like onion skin.
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