As a soil scientist for 33 years, I never really thought about the long history of soils on earth. I just focused on Siskiyou County’s forest soils. Siskiyou County has the most soil diversity compared to anywhere else in the United States. This is because our soil forming factors are extremely diverse. Our rainfall varies from 10 to 100 inches. Our elevations vary from 600 feet near Somes Bar to over 14,000 feet on Mt Shasta. Our landform slopes range from flat to extremely steep. Our geology includes granite, ancient sea sediments, serpentine, peridotite, lava flows, volcanic ash, stream and glacial deposits.
Earth began to form around 4.54 billion years ago (space.com; Aug 20, 2021). Earth’s soils occurred around 3.8 billion years ago when liquid water first condensed and starting eroding the Earth’s rocky crust (groundedinsoils.wordpress.com; Dec 1, 2020). Life in Earth’s oceans began around 3.8 billion years ago. These early microscopic organisms may have migrated to land as cyranobacteria around 3.5 billion years ago and formed surface soil crusts (groundedinsoils.wordpress.com; Dec 1, 2020). They were not the same as today’s soils. Soil formation at that time was controlled by parent material, topography, climate and time. These soil materials formed from the breakdown of rocks by physical and chemical processes. They were basically mineral particles of various sizes and voids containing gasses, mainly methane, nitrogen and carbon dioxide. These early soils lacked animals and organic matter. These soils, resembling current Martian soils, came and went for 3 billion years.
Fungi appeared on land around 1.3 billion years ago with land plants, such as mosses and liverworts, appearing on land about 700 million years ago. (science.psu.edu; Aug 8, 2001). Plants and soils became even more closely linked when plants developed roots some 400 million years ago (oeaw.ac.at; Aug 8, 2021). At this point, an essential part of the plant is entirely within the soil. This was the beginning of processes that created soils like we have today. Today’s soil forming factors are parent material, topography, biotic component (plants, animals), climate, and time. The earliest known land animal was a species of millipede, which lived 428 million years ago (fieldmuseum.org; Sept 23, 2015).
