![]() ![]() That is why he imagined the world was infinitely old. Consequently, to produce the enormous volume of rock we see on the earth, James Hutton assumed that geological processes continued over eons of time. These processes are reasonably small-scale compared with the size of the earth, and do not have much geological impact. We see magma erupt from volcanoes and crystallize into rock. We see sediment cementing into sedimentary rock. For example, we see rocks weathering and eroding and producing sediment. ![]() Consequently the diagram mentions processes that we see happening today. The basic philosophy of long-age geologists is that the rocks of the earth formed under conditions similar to what we see on earth at the present time. The metamorphic change is driven by heat and pressure. It can also change into different metamorphic rock but this is not shown on the diagram. Metamorphic rock can change into sedimentary rock, or igneous rock.The process of change is melting and crystallization. Igneous rock can change into sedimentary rock, metamorphic rock, or even different igneous rock.The process of change is weathering, erosion, deposition, compaction and cementation. Sedimentary rock can change into metamorphic rock, igneous rock, or even different sedimentary rock.This diagram shows how each kind of rock can change into other kinds of rock: After A portrayal of the rock-cycle concept Also shown is a box for “Sediment”, which is a step on the way to sedimentary rock, and “Magma”, or molten rock, which is a step on the way to igneous rock. It has a box for each type of rock, “Igneous rock”, “Sedimentary rock”, and “Metamorphic rock”. The figure at right shows a typical version of the rock cycle. The validity of the other cycles tends to give the long-age rock cycle credibility and implies that it is still operating, but it is not. The rock cycle, on the other hand, is envisaged to operate over timescales of millions of years, and as such it cannot be observed. These cycles operate over periods of weeks, months and years, and as such can be observed and studied. Many cycles exist in the natural world, such as the water cycle, the life cycles of insects, of other animals, and the nitrogen cycle. There are many versions of the rock-cycle concept around these days. (See articles on Hutton, on The Man Who Found Time and Siccar Point.) The aim of the cycle is to describe the relationship between the three basic rock types: igneous, sedimentary, and metamorphic. The original rock-cycle concept is credited to the Scottish physician James Hutton (1726–1797), who is regarded as a founder of modern, long-age geology. There are some aspects of the ‘cycle’ that are reasonable, which can be supported, and there are other aspects that involve eons of time, which need to be recognized and reinterpreted. The rock cycle is like many other concepts related to evolution and long ages. These slow, endless cycles Hutton imagined are similar to the Hindu concept of eternal cycles of nature. By presenting the rock cycle in a long-age framework naturally prepares students for other evolutionary ideas. As you discovered, geological concepts are introduced to students early in the curriculum within the long-age worldview. ![]() Yes, the rock cycle is a key concept in long-age ‘historical’ geology. Yet here is this concept introduced at an earlier stage, before any curricular discussion of biological evolution. How should Christians think biblically about it, and how might parents best handle it with their children as they are taught it at school? Is it one to which we can give qualified limited assent, except that it involves excessive extrapolation into the past? I was never taught any geology in school science, including A-level physics and chemistry. ![]() It seems to be a key concept in long-age historical geology. It includes the topic of the “rock cycle” to which a few CMI articles make passing references but none appear to give explicit treatment. when students turn 13 in the UK school system). We’ve just received the science curriculum my daughter will be following as she moves into Year 8 (i.e. ![]()
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