Historical Geology

The diagram to the right shows some of the possible structures. Note that the chain and double chain can be extended indefinitely in one direction and the sheet in two directions. A **silicate mineral** (or **silicate** for short) is a [mineral]( containing silicate structures; so silicate minerals

In this article we shall look at the most significant way in which geologists classify rocks. The reader should recall from [the article on minerals]( that a rock is an aggregate of one or more [minerals]( or [mineraloids]( ## Igneous, sedimentary, and metamorphic rocks ![The rock cycle.]( The rock

In this article, we shall present a brief overview of erosion and mechanical weathering. It is possible to be brief because the erosional processes involved will be discussed at length in subsequent articles, so there is no need to do more than sketch out the topic in brief. ## Definition Geologists

Chemical weathering is the breakdown of rocks into sediment by chemical processes. The reader who does not appreciate chemistry may skip the chemical formulas in this article and simply note the results of the reactions, as described in the summary section below. The results themselves cannot be ski

In this article we shall discuss soils, their formation, and their preservation as fossil soils (paleosols). It will be useful for the reader to be familiar with [the article on chemical weathering]( before reading further. ## Soil: what is it? The reader will of course have seen plenty of soil.

A **delta** is a fan of [braided streams]( and [sediment]( formed when a river discharges into a larger body of water: a sea or a [lake]( It will be useful if the reader has already read [the article on rivers]( before reading further. ## The dynamics of a delta As a river discharges into a larger b

This article contains a short general discussion of marine sediments and some important terms and concepts relating to this field. We need not in this article ask and answer our usual question: "How do we know?" since in the case of the facts given in this article the answer is simply and uniformly:

Once this mud has been deposited, it can be converted into stone by processes of [compaction]( [cementation]( and [recrystallization]( The main contributors to the ooze are coccolithophores and foraminifera. **Coccolithophores** are tiny single-celled organisms which cover themselves with tiny plate