Below the Amphitheater

6 routes · Granodiorite of Mount Evans batholith · 10,936 ft

Help locate these routes: survey the wall

What's here

5.7 to 5.11, but over half of these routes are 5.10.

1 5.7
3 5.10
2 5.11

Counted from the 6 climbs here that carry a grade. Shown only where there are at least 5 of them — below that the shape is noise.

How well located

Position on wall known 6

No route here has its own point yet. The map pin is the crag. At the wall? Survey it: 30 seconds per route.

The order of the climbs along this wall is known from the open catalogue, so a few surveys go a long way: standing at Sinapi, Ass Hat Seven (2 climbs, about 60 seconds) would place up to 4 more climbs between them. Survey the wall →

“Up to” because the estimate between two surveyed routes is only used when they turn out to be close enough together on the ground.

Rock, from the geologic map

Granodiorite of Mount Evans batholith. Mesoproterozoic, about 1,600 to 1,000 million years old.

Gray, massive to strongly foliated, coarse-grained, mostly porphyritic biotite-hornblende granodiorite, which ranges in composition from monzogranite to tonalite (Aleinikoff and others, 1993a). Locally contains as much as 5 percent of an aplite-pegmatite phase consisting of dikes and irregular-shaped bodies of massive to weakly foliated aplite and magnetite-bearing pegmatite. Formerly believed to be part of the Early Proterozoic Routt Plutonic Suite of Tweto (1987), due to petrographic and textural similarities to rocks of that suite and limited Rb-Sr data (for example, Bryant and Hedge, 1978). However, U-Pb zircon date is 1,442±2 Ma (Aleinikoff and others, 1993a), confirming emplacement with Middle Proterozoic Berthoud Plutonic Suite of Tweto (1987)

This is the map unit under this crag's map point, read from the 1:100,000 sheet (Kellogg and others, 2008, USGS Geologic Investigations Series 3000). The point can be a few hundred metres from the rock, a cliff often stands on the line between two units, and at that scale a line on the map is about 100 m wide on the ground, so the wall itself may be the neighbouring unit. Every crag on this unit: Granodiorite of Mount Evans batholith. Geology data: Macrostrat (CC BY 4.0), serving USGS and Colorado Geological Survey maps.

On the map since 1903

The USGS has mapped this ground since 1903. 28 historical sheets cover this crag's map point; the oldest is below.

Thumbnail of the 1903 USGS sheet covering Below the Amphitheater — **USGS 1:62500-scale Quadrangle for Georgetown, CO 1903** · U.S. Geological Survey · 1903 · 1:62,500 sheet
USGS Historical Topographic Map Collection · Public domain · the record · placed by its coordinates

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Hidden as soon as you tell us, everywhere it appears, before anyone reviews it.

Public domain, U.S. Geological Survey. The sheet shows the ground as the survey found it then, which is why a trail or road you know may be missing. Every sheet over this point, 1903 to 1983: USGS topoView.

Photographs near this crag

Taken within 1.5 km of this crag's map point and published under a licence that lets us show them, from Wikimedia Commons. The coordinates say where the camera was, not what it was pointed at, so some of these will be the creek or the trail rather than the rock.

Clear Creek County, CO, USA - panoramio (1) · Jacob Montgomery · 2010 · 581 m from the crag's map point
Wikimedia Commons · CC BY-SA · the record · placed by its coordinates

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