The Formation showed evidence of being the remains of what is called a “lahar.” Lahar is the term used by geologists to describe any type of mud flow or lava from a volcano. Lahars are often connected with volcanoes and glacial melting, but can also arise from other calamitous events such as earthquakes and even intense rainstorms.
The Blakely rocks were sedimentary rocks, breaking off in sheets. While there, I observed siltstone, and sandstone beneath my feet. We also observed fossils of petrified wood.
The next stop was the Renton Formation, an area that was mined heavily for coal during the first part of the last century. While I observed the rocks here, I identified them as sandstone, cemented by iron oxide.
At the Cougar Mountain site, I observed sedimentary rocks of many different varieties. Among them were sandstone, claystone, as well as oremite – an intrusive igneous rock.
Along the Coal Creek Parkway is the Tukwila Formation. The rocks I observed here were volcanic sedimentary rocks. I observed volcanic sandstone and volcanic conglomerate. The sandstone had a gray appearance and the conglomerate had horizontal layers.
When making a geologic map, geologists identify formations. Formations are shown using different letters and abbreviations. These formations are often named after a feature of the geography or the name of the town. A geologist must also measure the strike and dip of a formation. The strike is a compass direction where the rock layer is level. The dip consists of the compass direction that is perpendicular to the strike signified by a number in degrees.
In my results, I did not have very good information for the last stop, Stop 6. I had not observed anything about the Raging River Formation and knew little about it other than what was listed in the formation description.
For the first stop at the Blakely Formation, the strike was East-Northeast, with a dip that was 47 degrees North-Northwest. The second stop was at the Renton Formation. The geologic attitude measurement there had a strike of East Northeast and a dip of North-Northwest by 45 degrees.
The third stop, at the Tukwila formation, had a strike that pointed East-West and a dip directed North by 40 degrees. The fourth stop, at the Renton formation, had a strike that pointed East-West and a dip directed North by 40 degrees. The fifth stop had a strike that pointed North-South and a dip directed West by 45 degrees.
