Topic 2 Dynamics of Earth's Crust

Topic 2 Dynamics of Earth's Crust

2.1 Plate tectonics and seismic activity

Nature of science:

• Wegener's ideas about continental drift were initially explored and then dismissed for several decades by the scientific community? In the 1960s a revision of his ideas brought about a paradigm shift in the scientific community.

• Use of models as representations of the real world

Understandings:

• Earth has several moving plates outlined by intense earthquake activity at the edges of plates

• Mechanisms have been proposed for the movement of plates

• Movements include subduction, seafloor spreading, mountain building

• Plate movement over a hotspot has created the Emperor seamounts and the Hawaiian islands

• Marine trenches, island arcs, rift valleys, seamounts, mid-ocean ridges result from seismic activities due to plate tectonics

Applications and skills:

• Skill: modeling plate actions

• Skill: mapping plates and their movements on a globe

• Skill: determining an earthquake epicenter from seismic readings

• Limitations of models

2.2 Evidence of tectonics

Nature of science:

• Looking for patterns, trends and discrepancies

• Importance of verification among data sets in the building of a theory

Understandings:

• Evidence includes magnetic anomalies, temperature data, earthquake epicenter profiles, etc.

• Use of hotspot data in the Pacific to measure rate and direction of movements of the Pacific Plate

Applications and skills:

• Skill: examining data from edges of plates

• Data sets collected by magnetometers, seismographs, bathythermographs and core samplings can be analysed

• Skill: analysing of the velocity of plate movement

2.3 Tsunamis

Nature of science:

• Developing tools that can accurately detect and thereby be used to predict the magnitude and timing of an arriving tsunamis has been an engineering challenge.

Understandings:

• Tsunamis are generated by subsidence earthquakes, as well as submarine landslides and meteorites large enough to displace a large volume of water as well as volcanic eruptions and calving glaciers

• The wave characteristics change as the wave crosses the ocean and approaches shore. (in open oceans a wave may be less than a meter high with a period of 10 to 30 min and a wavelength of 100 - 200 km, but at a coast it may be 100 m high with shorter wavelengths as the energy of the wave is compressed into a smaller column of water.)

• Tsunamis are detected by DART ® with tsunameters that communicate with surface buoys and satellite communication

• Subduction tsunamis that occur near a coastline cause subsidence of the shore which complicates the effect of the tsunamis

Applications and skills:

• Skill: Use archival data to calculate the dimensions of a named tsunami.