Natural Science Tips
When it comes to Natural Science, we've been there, done that, now serving 116 tips in 15 categories ranging from Deserts to Weather.
Meandering Streams
Some streams run pretty straight, while others tend to meander - that is, they twist and wind their way along. Why is that?
Sometimes a stream needs all of its energy for down-cutting. Maybe it's cutting through rock that's hard to erode. Or maybe it's quite high, and has a long way to cut down to get to the right elevation to join the next stream. Then it uses all of its energy to cut straight down.
On the other hand, if the rock isn't very hard to erode, or if the stream is almost at the right elevation to join the next stream, it uses its energy for some downcutting but also for some side-cutting. That means the stream will develop twists and curves along the way, using its energy to erode back and forth and build a floodplain.
Where Rivers Come From
What makes rivers happen? Many rivers start as streams in the hills and mountains of a region. Raindrops gather in rills and collect to form creeks, which flow downhill and join to form larger and larger streams. Finally, when streams are at least 100 miles long, they're large enough to be classified as a river.
Where Rivers Come From
What makes rivers happen? Many rivers start as streams in the hills and mountains of a region. Raindrops gather in rills and collect to form creeks, which flow downhill and join to form larger and larger streams. Finally, when streams are at least 100 miles long, they're large enough to be classified as a river.
Porosity and Permeability
The spaces where the air and water reside are called voids or pores, and the amount of space a soil has for storing air or water is its porosity. If the pores are not connected well, a soil can store water but doesn't transmit it well - that is, it can be porous but not permeable. A soil with pore spaces that are well-connected, on the other hand, is porous AND permeable. It can store water, but it can also transmit the water. A soil that is porous and permeable, like a sandy loam, is much better for growing plants than a very porous soil that isn't permeable - like clay, which has up to 50% porosity but doesn't transmit the water well.
Soil Defined
"Soil" means different things to different people. Soil scientists use it to mean unconsolidated granular material that has enough organic matter in it to support plant growth. Engineers use it to mean earth material that can be bulldozed away, without having to use dynamite.
Geologists use the term either way.
Earthquake Prediction
A great deal of research has been devoted to the topic of earthquake prediction. It's not easy, though, and the best we can do is use statistics to determine which areas are probably due for a quake soon. Earthquake hazard maps delineate areas with the greatest probability of experiencing significant shaking within the next 50 years.
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| Christina Chan |
