Soil Science 100 ID__________________________

Take home exam Lab Section___________________

First Midquarter exam

Monday 21 October 2002

Fill in the blank spaces with master horizon and subordinate horizon designations. This is an open book exam, but you must complete the exam by yourself. This portion of the exam is due at the start of the in-class exam period on Monday 21 October. Late exams will not be accepted.

Oe--1/2 inch to 0; partially decomposed leather oak leaf litter mixed with much medium size gravel; abrupt smooth boundary. FULL CREDIT FOR O DESIGNATION (1.5)

A--0 to 3 inches; brown (7.5YR 4/4) gravelly loam, very dark brown (7.5YR 2/2) moist; strong very fine granular structure; soft, very friable; few very fine and fine roots; many very fine and fine pores; about 35 percent rock fragments; slightly acid; abrupt smooth boundary. (1 to 4 inches thick) FULL CREDIT FOR A DESIGNATION (1.5)

BAt--3 to 10 inches; brown (7.5YR 4/4) very gravelly clay loam, dark brown (7.5YR 3/2) moist; weak medium subangular blocky structure that parts to strong fine and very fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine and medium roots; many very fine and fine pores; thin nearly continuous clay films lining a few pores; about 40 percent rock fragments; neutral; clear irregular boundary. (3 to 7 inches thick) FULL CREDIT FOR EITHER BAt, (3), Bt1 if followed by Bt2

Bt--10 to 19 inches; brown (7.5YR 4/4) very gravelly clay loam, dark brown (7.5YR 3/2) moist; moderate medium subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; some clay films in pores, but clay films mainly as bridges between mineral grains; about 40 percent rock fragments; few angular cobblestones; neutral; abrupt irregular boundary. (6 to 9 inches thick) FULL CREDIT FOR Bt or Bt2 if Bt1 above (2)

R--19 to 24 inches; fractured greenish blue serpentine rock; a few cracks more than 4 inches apart filled with soil from above; thick clay films on rock faces in fractures. FULL CREDIT FOR R (2)

No partial credit on O horizon. Ignore subordinate distinctions on O. No partial credit on A. Reduce by 1/2 point if subordinate designations are used. Partial credit on the third and fourth horizons are at your discretion. No partial credit on R horizon.