Science · Earth and Space Science
Chapter 1: Earth as a System
The interesting part is where they meet.
In the winter of 1965–66, scientists cut every tree in one 39-acre (16-hectare) valley at Hubbard Brook, New Hampshire, and left the logs where they fell. Nobody touched the stream, yet the next year it carried about 40% more water and about 40 times as much nitrate.
How did cutting trees change a stream nobody touched?
Make your guess to turn the page.
Still to come: 10 pages · Lab · Words to Know · What We Learned · 4 questions · Explain It in Writing · Open Questions
The idea this lesson is working on — Students picture the four spheres as stacked layers or separate places, which makes a clear-cut look like a change to the biosphere alone. The book sets that against Hubbard Brook, where cutting trees changed a stream, soil and air nobody touched, and against Saharan dust feeding the Amazon. Ask: which sphere did that matter come from, and which one did it cross into? The idea to reach is that spheres are categories of material and processes are transfers between them.
The interesting part is where they meet — Geosphere, hydrosphere, atmosphere and biosphere are a way of organizing study. Almost every phenomenon worth explaining — soil, weather, erosion, climate — happens at an interface between two of them. The Hubbard Brook Ecosystem Study (Bormann and Likens) began in 1963; Watershed 2 was cut in 1965–66 and kept bare with herbicide for three summers. The dust figures are from Yu et al. (2015), from CALIPSO satellite lidar, 2007–2013.
Nothing belongs to only one — A tree is biosphere rooted in geosphere, drawing hydrosphere and exchanging with atmosphere. The divisions are analytical conveniences, not boundaries in the world, and many schemes add a cryosphere for ice.