For this exercise you will use the same set of 5 pyroclastic fall deposit samples which you examined in your last exercise.  This week you will use a set of stacked screens with 1 phi intervals to make a grain-size analysis.  We will not use a mechanical shaker because the samples were small and do not necessarily represent a good sampling of the deposit.  However, they should display the main characterisitcs of the deposits.  You should work in groups to perform the analysies and tablualte the data.  Then you will individually plot the histograms of the samples and determione the Inmann statistics using the SFT code.

Use a stereo microscope to examine the 0 phi and 2 phi fractions of each sample to estimate the percentages of the various components.

Finally you should compare the results from this study with those obtained by visual inspection in your last lab and record any new conclusionsthat you reach, if appropriate.

Comments on the eruption characteristics and differences between samples, especially compare COT-0301 A, B, & C.

1.COT-0301A

2.COT-0301B

3.COT-0301C

4.COT-0304

5.STU-9328

All samples labeled COT came from Cotopaxi Volcano, Ecuador.Samples COT-0301 were collected at the same outcrop about 10 km from the summit.The letters A-C refer to collection levels from the base to the top of the exposure.Samples A & B are the lower and upper parts of the same depositional bed.A soil separates sample b from sample C.Sample COT-0304 was from the summit of the volcano.Sample STU-9304 comes from the 1907 eruption products of Stubel Volcano, Kamchatka.