(Courtesy Oregon Timber Trail) 1  Since 1992, hikers have been able to traverse Oregon north to south using the Pacific Crest Trail, which traces the Cascades from the Bridge of the Gods to the California state line. This summer, you can finally bike across the state, from Hood River to the mines of Modoc County, Calif.
Definition: A delta wave is a type of high amplitude brain wave found in humans. Delta waves have a frequency from one to four hertz and are measured using an electroencephalogram (EEG). These brain waves are thought to emerge from the thalamus and are generally associated with slow-wave sleep (during stages three and four of the stages of sleep.
Definition of Mechanical Waves. A mechanical wave is a wave that is a vibration in matter, transferring energy through a material. Not all waves are like this. For example, electromagnetic waves such as visible light are not mechanical because they can travel through the vacuum of space to reach us from the sun. Mechanical waves include water waves, sound waves, earthquake waves, and many more. Like all waves, those of the mechanical variety have peaks, or crests, and troughs. They also have a frequency, which is the number of waves that pass by per second, and a wavelength, which is the distance from one peak to the next, or one trough to the next.