Passage II

A lahar is a flow of water-saturated volcanic ash and rock. A lahar deposit, formed once the flow stops, consists of clasts (rocks having diameters ≥ 16 mm) embedded in a matrix (a mixture of particles having diameters ≤ 8 mm).

A sample of a lahar deposit was collected at each of 7 distances from a volcano's crater. For each sample, Figure 1 shows the percent by mass of the clasts by composition, and Figure 2 shows the percent by mass of the matrix by particle size class. For the 7 samples combined, Figure 3 shows the cumulative percent by mass of clasts and matrix particles, or of clasts alone, as diameter decreases.

9. Consider the information in Figures 1 and 2 about the lahar deposit sample collected 270 km from the volcano's crater. Clasts of which composition accounted for more than 50 percent by mass of the clasts in the sample, and matrix particles of what size class accounted for more than 50 percent by mass of the matrix in the sample?

Answer and Explanation

Your Answer is

Correct Answer is D

Explanation

Corresponding to figure 1, the abscissa is 270km, and the content of andesite exceeds 50%;

Look at figure 2, the abscissa is 270km, and the proportion of sand exceeds 50%