Chapter 1

CHALK AND LIMESTONE
1-6. Chalk and limestone are slippery when wet. Limestone is usually solid; however, conglomerate type
stones may be loose. Limestone has pockets, face climbing, and cracks.

SLATE AND GNEISS
1-7. Slate and gneiss can be firm and or brittle in the same area (red coloring indicates brittle areas).
Rockfall danger is high, and small rocks may break off when pulled or when pitons are emplaced.

SANDSTONE
1-8. Sandstone is usually soft, causing handholds and footholds to break away under pressure. Chocks
placed in sandstone may or may not hold. Sandstone should be allowed to dry for a couple of days after a
rain before climbing on it―wet sandstone is extremely soft. Most climbs follow a crack. Face climbing is
possible, but any outward pull will break off handholds and footholds, and it is usually difficult to protect.

GRASSY SLOPES
1-9. Penetrating roots and increased frost cracking cause a continuous loosening process. Grassy slopes
are slippery after rain, new snow, and dew. After long, dry spells, clumps of the slope tend to break away.
Weight should be distributed evenly; for example, use flat hand push holds instead of finger pull holds.

FIRM SPRING SNOW (FIRN SNOW)
1-10. Stopping a slide on small, leftover snow patches in late spring can be difficult. Routes should be
planned to avoid these dangers. Self-arrest should be practiced before encountering this situation.
Beginning climbers should be secured with rope when climbing on this type surface. Climbers can glissade
down firn snow if necessary. Firn snow is easier to ascend than walking up scree or talus.

TALUS
1-11. Talus refers to rocks larger than a dinner plate, but smaller than boulders. They can be used as
stepping-stones to ascend or descend a slope. However, if a talus rock slips away it can produce more
injury than scree because of its size.

SCREE
1-12. Scree refers to small rocks from pebble size to dinner plate size. Running down scree is an effective
method of descending in a hurry. A Soldier can run at full stride without worry―the whole scree field is
moving with him. Climbers must beware of larger rocks that may be solidly planted under the scree.
Ascending scree is tedious. Scree does not provide a solid platform and will only slide under foot. If
possible, avoid scree when ascending.

ROCK CLASSIFICATIONS
1-13. Rock is classified by origin and mineral composition.

IGNEOUS ROCKS
1-14. Deep within the earth’s crust and mantle, internal heat, friction and radioactive decay creates
magmas (melted silicate minerals) that solidify into igneous rocks upon cooling. When the cooling occurs
at depth, under pressure, and over time, the minerals in the magma crystallize slowly and develop well,
making coarse-grained plutonic rock. The magma may move upward, propelled by its own lower density,
either melting and combining with the overlying layers or forcing them aside. This results in an intrusive
rock. If the melt erupts onto the surface it cools rapidly and the minerals form little or no crystal matrix,
creating a volcanic or extrusive rock.

1-2

TC 3-97.61

26 July 2012