On a beautiful early summer day, my wife and I, and a good friend of ours, were treated to an outstanding geologic tour of RMNP led by Ranger Rod. My friend and I are geologists who recently retired in the Fort Collins area. We have a reasonably good level of knowledge of the geology of Northern Colorado that we have gained from numerous hikes in the area. My wife is not a geologist but she is a geology enthusiast. Our tour started outside the park with an overview of the metasedimentary rocks along Hwy 34 in the lower portion of the Big Thompson Canyon, and then a stop along CR43 to look at an outstanding pegmatite outcrop on the way to Glen Haven. Once in the park we learned about the granite exfoliation domes and Tors that make up the area around Lumpy Ridge. We were then treated to an overview and a tour of the role glaciers have played in shaping the landscape of RMNP. With the use of a fantastic hand-painted panoramic hiking map of RMNP (painted by James Nehues of ski area map fame), Rod pointed out a number of long glacial valleys, cirques and moraines including some very impressive lateral and terminal moraines that we had not noticed during previous visits to the park. A stop to see the man-caused alluvial fan from the 1982 Lawn Lake dam failure, and hear the story of how it blew through the Fall River Valley lateral moraine, was very interesting. We continued on up Trail Ridge Road with a stop at Hidden Valley to see the 1 billion year old Iron Dike that we had never seen or heard of before. We then continued up to the higher country to get an overview of the Never Summer Mountains and to learn that they are the glaciated remnants of magma chambers formed "only" 23 million years ago. The tour ended with a short walk around Sprague Lake with impressive views of Long's Peak. What a great day with a great guide. Rod's knowledge of the geology of RMNP is tremendous and his ability to tell the geologic story in a way that geologists and non geologists alike can easily understand, was impressive. I highly recommend this guided trip for geologists and curious non geologists as well.