For how many years now I've been going to Salt Lake District Park twice a week for soccer practice, but I've never noticed or took the time to look at my surroundings.It's a park, what else could there be?Only after taking this class I started to think about the hills, the lake, and the other features of the park.
The first thing that caught my eye when I went there for observations was a sign that read, “Warning, Falling Rocks.”I never noticed that before.I then looked up at the hills to see if there were any loose rocks or other material that could fall.I found small loose rocks at the base of the hill and lying against the hill.As I looked south over to the next crater I noticed a slump in one side of the crater.It looks as if there was a landslide or that side of the crater was blown out.The depression has vegetation but it is not as green as the other parts of the crater and hills.It's hard to tell if a landslide really did occur there though because the mountains and hills overlap each other and cross over each other, and the hill is kind of far away.
Going to the top of the park I found part of the Aliamanu crater.It sits right above the upper field of the park.Looking at the rim I noticed that the crater was step like with the top step made up of mostly dirt and as you go down the lower steps are made up of mostly rock.The rocks were mostly brownish in color, but the lower layers were more grayish with white chunks and specs in them.I noticed one very unusual whitish rock embedded in the gray rock on the lower levels of the hill.This rock was the only rock that I saw of it's kind and was very smooth, almost looking like a gel or sap.There were also some darker black areas in the rock, but they were mostly on the upper layers or steps of the crater.I don't know if the dark areas were from fires or if they were different rocks embedded in the hill.The steps had horizontal layers embedded in them.Some were just grooves and others were whitish in color.You could see the cracks and depressions from water erosion that has taken place over the years from rain dripping down the hill.The lines in the rock and different steps may have been from a rise and fall of water level that was once there.
The entire Salt Lake area has good green vegetation.The park obviously is going to be green but the hillsides are also green with grass and small bushes.The park slopes downward moving away from the Aliamanu crater rim.At the bottom is a small lake right next to the country club.
I noticed from the freeway and the roads leading to the park that you can see what I think is Makalapa crater and Salt Lake crater.You can also see what I think were parts of the other small craters in the Salt Lake area from the road right off of the freeway.All the hills seemed to have the same step like formation and the same rocks embedded into the hillsides.As I looked north towards the Koolau I was looking at the valleys.I was thinking about how once larger rivers flowed through those valleys.I also noticed how in the Halawa area, it looks as if the rocks and make up of the cut away hill looks the same as the hills in Salt Lake.They also are step like.
The Salt Lake group of volcanoes are tuff cones that feature low ash cones with broad rimes and wide craters.The explosions of these volcanoes were powerful and explosive because of the rising magma that meets water underground at shallow depths and makes steam.The steam increases the pressure and it is released suddenly making a very powerful explosion.The explosion burst through an old coral plain that was once there from a higher sea level.The volcanoes in this area are famous for their xenoliths and fragments of the earth's mantle, as large as 6 inches.Some of these xenoliths contain red garnet.There are only few other places in the world that you can see rocks that are certain to be from the mantle.There were no lava flows outside of these volcanoes although there were some found inside the crater.The volcanoes here mostly exploded and sent ash into the air.The ash then covered and settled on the surrounding areas.The volcanoes caused the Moanalua Stream and the Halawa Stream to find change their course to the sea.They once ran parallel to each other coming out of their respected valleys to the sea, but now go around the volcanoes.These volcanoes in the Salt Lake area exploded later in time and are similar to Diamond Head, Punchbowl, and Koko Head.I noticed however that these other volcanoes can be seen much easier than the volcanoes in Salt Lake.
After doing this field trip report I started to notice and to think about other hills and mountains on our island.I never used to think about how they were made or what the composition of it was, but now I find myself thinking about those kinds of things.