I have had the opportunity to accompany Chris Gentile, a graduate student at UCR on a day trip up to the Hogback landslide in the San Gabriel mountains. He is primarily studying the above mentioned slide in order to date it. To do this, we collected large bags of quartz-rich rock. This rock must be quartz-rich and exposed to daylight for practically the whole day in order for this type of dating to be accurate.
The Beryllium 10 isotope is consistently being built-up in quartz in the rocks by the bombardment of radiation from the sun. By calculating the amount of sun each day throughout the year, we can calculate the amount of Beryllium 10 added to the rock for a given amount of time. Chris uses a digital theodolite on an iPad to do these measurements. This involves pointing the camera towards the peaks of the surrounding mountains at 15° increments in a circle at the point where we collected the rock to be studied.
It was tough to find suitable boulders with surfaces that fit all of the requirements. They must have a surface that has not seen too much weathering and erosion because the face we collect will not be true to its age. The surface must also have abundant quartz, and must not be surrounded by trees or other obstructions that would block sunlight. Another difficulty was actually obtaining the samples. We had to use a rock hammer and chisel to break pieces off to collect.