In the last few days of the Geology module, students learned about the climate system in East Africa as a foundation for the sedimentology of Lake Turkana. Dr. Christopher Lepre, the module instructor from Columbia University, started with how the earth moves and how it affects the heat distribution between different climate zones, as well as how the movement of air masses affect seasonality around the globe. East Africa typically has two dry seasons and two wet seasons alternating each year. Currently, we are at the end of the long dry season and the landscape has been looking pretty barren. However, we were lucky to have some rain in the last few days and students had a chance to enjoy some (relatively) cool air brought by the storms. Some said that it had something to do with the El Niño and we may expect some more rain in the coming weeks. Let’s hope that the rain and potential flooding are not going to affect our upcoming field work!
The development of the Great Rift Valley of East Africa also had significant influence to the hydrology of the ancient Lake Turkana. There were substantial changes in the drainage pattern of the Turkana Basin. Lake Turkana was once connected to the Nile river system, which explains the presence of Nile species in the lake today, including Nile perch and tilapia. The lake had higher levels in some periods in the past and in some other periods, there were no lake but instead, rivers and floodplains running through the Turkana Basin. All these changes of the ancient times have been recorded in the lake/river sediments.
Another important component of the Geology module has a lot to do with rocks and sediments. In class, Dr. Lepre went through important geological terms with us starting from the minerals that make up rocks to how different types of rocks are formed in geological processes. Volcanoes associated with the rifting activities created a lot of igneous rocks that can be found all over the Turkana Basin. Sedimentary rocks make up a majority of the rocks found in the basin today because of the constant erosional and depositional processes happening both in the past and present.
Apart from a significant amount of time spent in the classroom, students also went out for a couple of field trips, which turned out to be very successful. We learned how to mark and record stratigraphical information at outcrops by using standard geological tools. Through a lot of practicing, students are now very comfortable with GPSs and compasses, no worries of getting lost in an exotic desert (I guess)!
In the field, we also learned about how to identify different types of sediments and how they are associated with the carrying capacity of flowing water: faster water can carry larger and heavier particles, slower water carries finer particles. Thanks to the rain of the previous night, there was water in some ephemeral streams where we visited during our field expedition. Dr. Lepre showed us how to identify water level and flow speed at different spots of the riverbed where features of flow were preserved.
There were several other interesting things than rocks that we found in the field! See if you can identify them!
Thank you very much for your participation! Now it is time to reveal what the mysterious objects are!
Mysterious object 1: Skull of a monitor lizard
Mysterious object 2: A gigantic dung beetle
Mysterious object 3: Coprolite (fossilized feces!)
Mysterious object 4: Sand lizard
Mysterious object 5: Horn of an oryx
Mysterious object 6: Fossil catfish skull
Stay tuned for more!