soil strata
101Cambrian Period — Oldest time division of the Paleozoic Era. During the Cambrian, 543–490 million years ago, there were widespread seas and several scattered landmasses. The largest continent was Gondwana. The average climate was probably warmer than today, with… …
102Devonian Period — Interval of geologic time from 417 to 354 million years ago; it was the fourth period of the Paleozoic Era. During the Devonian, a giant continent was situated in the Southern Hemisphere (see Gondwana), and other landmasses were located in the… …
103roads and highways — ▪ transportation Introduction traveled way on which people, animals, or wheeled vehicles move. In modern usage the term road describes a rural, lesser traveled way, while the word street denotes an urban roadway. Highway refers to a major… …
104dipteran — /dip teuhr euhn/, adj. 1. dipterous (def. 1). n. 2. a dipterous insect. [1835 45; DIPTER(A) + AN] * * * Any member of the more than 85,000 species in the insect order Diptera (the two winged, or true, flies), characterized by the use of only one… …
105Intermontane Plateaus — Physiographic regions of the U.S. Interior See:legend For purposes of description, the physical geography of the United States is split into several major physiographic divisions, one being the Intermontane Plateaus. Please refer to the Geography …
106Social class in the United States — A monument to the working and supporting classes along Market Street in the heart of San Francisco s Financial District Income in the United States Affluence in the …
107Stratum — In geology and related fields, a stratum (plural: strata ) is a layer of rock or soil with internally consistent characteristics that distinguishes it from contiguous layers. Each layer is generally one of a number of parallel layers that lie one …
108Geoarchaeology — is a sub field of archaeology which uses the techniques and subject matter of geology and other earth sciences to examine topics which inform archaeological knowledge and thought.Geoarchaeologists study the natural physical processes that affect… …
109Shaft construction — concerns the building of vertical openings such as Raises and Shafts. Shafts are vertical openings used for supplying equipment, personnel, and support systems to the horizontal tunnel where the pipeline is installed. They can be temporary or… …
110cave — cavelike, adj. /kayv/, n., v., caved, caving. n. 1. a hollow in the earth, esp. one opening more or less horizontally into a hill, mountain, etc. 2. a storage cellar, esp. for wine. 3. Eng. Hist. a secession, or a group of seceders, from a… …
