some towns so object to the red color that officials have switched to buying sand from gravel pits in the Uplands, where the sand is a light tan.) Red soils are characteristic of tropical and subtropical climates but unusual in so cold an environment as Connecticut. The striking color comes from the soft red-brown rock that underlies most of the Central Valley and gave rise to the soil. This attractive rock is commonly called brownstone or, in the rather arcane language of geologists, arkose.

Brownstone is an example of sedimentary rock, one of the three main types of rock. (The others, igneous and metamorphic rock, will be discussed later.) Sedimentary rocks form whenever piles of sediment left by erosion are cemented into stone. Erosion works its nutpick against the entire land area of the world and, in its slow, methodical way, provides the raw material needed to make sedimentary rocks. The formerly loose sediments now locked inside brownstone were deposited in the Central Valley by the nameless streams that eroded the Uplands millions of years ago. In Connecticut, sedimentary rocks are found almost exclusively in the Central Valley.

Brownstone, the product of the erosion of other rocks, is itself easily eroded. For millions of years, streams have plucked away at this soft rock, forming the broad Central Valley lowland. Glaciation, too, put its muscle to the rock, often gouging deep into the brownstone. Lake Saltonstall, east of New Haven, is just such a glacial gouge; at its deepest point, the lake lies 85 feet below sea level. Another is the Farmington River Valley in Simsbury; here the brownstone bedrock now lies 400 feet below the surface, buried by more recent sediments.

The effects of glaciation can be read from almost all of the Central Valley landscape. Although most geologists do not believe that glaciation has drastically changed the shape of Connecticut's hills and valleys, it did clean things up a bit. The earlier blanket of soil was swept away and weaker rocks were scraped off the bedrock crust. Glaciers are not tidy housekeepers, though, and the refuse from all this sweeping and scrubbing - glacial drift - was strewn across Connecticut. Glacial drift probably covers more than 99 percent of Connecticut's bedrock surface.

There are two main types of drift: stratified drift and till. Dig a hole in each of the two types and you will quickly discover their essential

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