Geology Reference
In-Depth Information
1
INTRODUCTION AND OCCURRENCE
Igneous rocks occur in almost all environments at the Earth's surface as
volcanoes and their dispersed products, and within the crust and mantle as they
form the pathway from which the Earth cools from it's hot interior. The
products of igneous activity not only provide key information about the
evolution of the Earth through time, they can be used as key stratigraphic
markers, form the basis of our understanding of the Earth's chronology and
can be found to have striking effects on our planets climate. From the beauty
of diamonds, the wonders of erupting volcanoes and the polished rocks which
adorn buildings all over the world, man has had a fascination with igneous
rocks as far back as we can trace. The key basis from which we can understand
igneous rocks and their systems is from detailed fieldwork and observation.
This guide aims to provide the basic information and tools to enable earth
and engineering scientists from a variety of backgrounds to investigate the
wonderful world of igneous rocks in the field.
1.1 The Importance of Fieldwork
The most fundamental observations that you can make within the earth sciences
are in the field. Here we are able to characterise the occurrence of earth materials
in situ
, in relation to their surroundings and within the context that will underpin
any further investigations of the rocks in the lab. In short -
Fieldwork is the basis
of all geological studies
. As such it is important that a person who wishes to
understand rocks is proficient in the field. Whether one is studying igneous,
sedimentary or metamorphic rocks the fundamentals of the fieldwork are more
or less that same and indeed one may need to address all three major types of
rock in the same field locality. It should be noted that there are many instances
in which expensive geochemical and geophysical data have been misinterpreted
through incomplete knowledge of basic field relationships. Therefore,
if the
appreciation of field geology is poor, then all studies based on collected samples
and field measurements will be equally poor
. Conversely,
good appreciation of
field geology forms the basis of good geological interpretation
.
As a good field scientist you will need to have a background of basic skills to
enable you to make the correct detailed observations that will in turn lead to clear
