Gigantic pulsating blue-green ball of light rose up over a ridge, hovered and then rose straight up at high velocity until out of sight

While walking down a dark logging road with a friend at 4:30am in a rugged area of Snohomish county WA one summer night, we noticed a dim light high above on a ridge.  We thought at first that there was a car up there, but then became confused because of the strange way the light was acting. It kept growing stronger over a period of about 15 seconds.  We then thought maybe it was a helicopter, but there was a noise. Not even a noise really. I've only been able to describe it as more of a vibration operating outside the range of human hearing. It seemed to have the properties of a very low cycle oscillation and a very high oscillation at once. It was very eerie. Anyway, as the light grew brighter (around 15 seconds elapsed so far) This gigantic blue-green ball appeared over the ridge. It seemed to shimmer and pulsate a blue-green light.  It was very bright and light up the valley(mountainous logging type area) we were in. It made the hair on the back of my neck stand up and tears well up in my eyes. It was clearly a gigantic glowing sphere. It hovered there for around a minute, it was about 1-2 miles and it wa huge. I'm guessing at least 1/4 mile across. I mean, it was ridiculous. It lit up the entire area like day. After standing there in complete and utter awe of of this thing for around a minute saying things like, "holy ((deleted))!", my friend and I began to run down the road in the direction of the sphere. Believe it or not, we were yelling,"take us with you!". We got about 50 yards and the mammoth sphere started to rise straight upwards.  Its speed seem to increase at an exponential rate (slowly, then faster and faster). The time from the begining of it's accent until it was completly out of sight(on a partly cloudy night) was about 3-4 seconds. It moved very very fast the last second or so. It was very dis-appointing. For a moment we both thought we could make it up that ridge. I think I was in some variation of shock. It wasn't until the sun came up that I could really see how big the ridge was that it came over and the surrounding area. It was then that I concluded that it must have been about 1/4 mile wide. I was 19 when this happened, 29 now working at microsoft. :( This event has been on my mind for a long time, I think about it often. I went to alta-vista this evening and typed "blue-green ball", and voila! here I am! Please take note that the date is really sometime in the summer of '90