Chapter 2, Problem 1CT

Plate tectonics works today in the same way as in the past. Can you project the future positions of the continents by looking at a map of their present positions and the positions of the mid-ocean ridges (see Fig. 2.5)? Which oceans are growing and which are shrinking? Where will new oceans form?

FIGURE 2.5 The major features of the sea floor. Compare this map with Figure 2.6.

Summary Introduction

To predict: The future positions of the continents by looking at the map of their present positions and the positions of the mid-ocean ridges.

Introduction: The continents in the earth’s crust or plates that float on the mantle portion of the Earth are called plate tectonics. The movement of plate causes formation of the mountain and continents over a millions of years that result in the geographical changes of the Earth.

Explanation of Solution

Plate tectonics are the lithospheric plates composed of continental and oceanic lithosphere. Refer to Fig. 2.5, “The major features of the sea floor”, in the text book. The future positions of the continents are given in Table 1.

Tabular representation: The following table shows the future positions of the continents.

Table 1: The future positions of the continents

Continents	Future positions
North and South America	Farther west toward the Pacific Ocean
Europe and Asia	Farther southeast
Australia	Farther northeast
Africa	Farther east

Summary Introduction

To determine: The oceans that are growing and shrinking.

Introduction: The continents in the earth’s crust or plates that float on the mantle portion of the Earth are called plate tectonics. The movement of plate causes formation of the mountain and continents over a millions of years, which result in the geographical changes of the Earth.

Explanation of Solution

Plate tectonics are the lithospheric plates composed of continental and oceanic lithosphere. Refer to Fig. 2.5, “The major features of the sea floor”, in the text book. The shrinking ocean is Pacific Ocean (expected to be narrower) and the growing ocean is Atlantic Ocean (expected to be wider).

Summary Introduction

To determine: Where will the new oceans form.

Introduction: The continents in the earth’s crust or plates that float on the mantle portion of the Earth are called Plate tectonics. The movement of plate causes formation of the mountain and continents over a millions of years, which result in the geographical changes of the Earth.

Explanation of Solution

Refer to Fig. 2.5, “The major features of the sea floor”, in the text book. The edges of several plates are formed by the mid-ocean ridges.  At this point, the lithospheric plates move apart to form the new oceanic lithosphere (new sea floor). If the plate contains a block of continental crust, the plate moves away from the ridge, and the continent is carried along with the plate.