Mount Hood's last major eruption occurred in the 1790's not long before Lewis and Clark's expedition to the Pacific Northwest. In the mid-1800's, local residents reported minor explosive activity, but since that time the volcano has been quiet.
Signal Colors and Their Meaning. The colors used in today's signals are green, yellow, red, lunar, and white (remember, we're talking about signals in North America). The color of a signal tells the engineer what he has to do, the location of that color, determines the speed at which he is allowed to do it.We will get to the speed thing in a minute.he colors used in today's signals are green, yellow, red, lunar, and white (remember, we're talking about signals in North America). The color of a signal tells the engineer what he has to do, the location of that color, determines the speed at which he is allowed to do it. We will get to the speed thing in a minute.
Color (American English) or colour (Commonwealth English) is the characteristic of human visual perception described through color categories, with names such as red, yellow, purple, or blue. This perception of color derives from the stimulation of cone cells in the human eye by electromagnetic radiation in the spectrum of light. Color categories and physical specifications of color are associated with objects through the wavelength of the light that is reflected from them.