Notes of Lessons: Physical Science, Class IV
Subject: Geology • Group: Science • Class IV • Time: 40-45 minutes
By J. H. Smith
The Parents’ Review, 1909, pp. 793-794
Objects
I. To give the girls a brief history of the formation of rocks in our own neighbourhood.
II. To increase their interest in geology, so that they will want to study in more detail for themselves the formation of these rocks.
III. To make clear to them a few geological terms, that will help them in this study.
IV. To give the girls some conception of the wonderful changes through which the world has passed, before it was made fit for the habitation of man.
Lesson
Step I.—Ask the girls why the geology of our district should be particularly interesting, supplementing their knowledge by speaking of (a) Comparative age of the rocks; (b) Interest of the fossils.
Step II.—Show them on a geological map the general strike of the rocks all over England and Great Britain. Explain the terms “strike,” “outcrop” and “dip,” if necessary.
Step III.—Give the girls a short history of the old rocks represented in our district.
(a) A thick layer of sedimentary rocks, laid down under shallow water. We can tell this by the nature of the rock and the fossils found in it. Time taken, 1 1/2-6 million years. Thickness, 10,000-12,000 feet.
(b) Volcanic action from below, caused by internal changes in the earth, caused hot lava to force its way through the layer of sedimentary rocks, which it soon covered with its flow of lava and hot ash. Intervals of action and inaction during 3/4-1 1/2 million years, which caused rock to be laid down in layers, piling up to between 11,000 and 15,000 feet above sea level. Compare with Mount Etna. Show scale with comparative heights of mountains. Ask how we can tell volcanic rock.—By its similarity to rock thrown out of volcanoes active at the present time.
(c) This whole mass of rock (sedimentary and volcanic) sank gradually, till under sea level, and a new formation of rock was made. What kind of rock will it be as it was laid under water?—Sedimentary. The land at this time was being continually heaved up and sinking again, till five different layers of sedimentary rock were formed. Distinctive fossils in each layer. Whole bed, called “Upper Silurian” (from Silures), about 14,000 feet thick.
(d) These three formations of rock, gradually raised up in the N.W. of the Lake District, until even the lowest layer appeared. At the same time denudation affecting the surface and carrying off whole masses of rock. What are the agents of denudation?—Frost, snow, rain. In this way we have the oldest rock appearing at the surface. The mountains and hills we see now, caused by lateral pressure from N.E. and S.W. Lateral pressure caused by contraction of centre of the earth. Ask girls to narrate.
Step IV.—If the rock were raised up on the N.W. side, in what part of Lake District must we expect to see oldest rock?—N.W. Show geological map, and ask girls to calculate roughly area we see of each formation. Tell them the names of the formations:—
(1) Skiddaw Slate.
(2) Volcanic Series of Borrowdale.
(3) Upper Silurian Series, beginning with Coniston Limestone, which they tested in geology walks. Fossils they found were in the next stratum.
Step V.—Ask the girls to put the names of the different series in the maps provided.
Step VI.—Ask the girls, from what they know of the scenery, the character of the different formations we have studied. Show them some pictures to help what they remember themselves.
Step VII.—Read them a quotation from Ruskin, on Mountains.