When Alfred Wegener argued early last century that all continents had once been

Question

When Alfred Wegener argued early last century that all continents had once been connected by had cracked and moved part, he had little to support his theory besides the shape of the continents. Today, much evidence supports the theory of continental drift, not the least of which is an accurate measurement of increasing or decreasing distances between fixed points on various plates. Not only are horizontal movements on the order of centimeters per year measureable with modern equipment, but the much slower lifting of mountains is also measured with great accuracy. What modern equipment is capable of making such fine measurements on shifting surfaces, and when was it developed? When a plate is said to move northeast at one inch per year, to what is the movement relative? Besides these readings, what other evidence have scientists found that all the Earth's landmasses were once connected? And which mountain ranges are still being formed, which are eroding, and when will the Great Rift Valley - a divergent fault - become an inland sea?

Explanation / Answer

Scientists use a network of satellites called the global positioning system (GPS) to measure the rate of tectonic plate movement GPS measures rate of movement in north, east, and vertical directions that are combined to give information of the location in 3-D space. The US began the GPS project in 1973 to overcome the limitations of previous navigation systems.

When we use the term "relative plate motion", it means the motion of one plate relative to another plate, so at least two plates are involved.

1.Before GPS, Alfred Wegener found that large-scale geological features on separated continents often matched very closely when the continents were brought together. For example, the Appalachian Mountains of eastern North America matched with the Scottish Highlands, and the distinctive rock strata of the Karroo system of South Africa were identical to those of the Santa Catarina system in Brazil.
2.When the different land masses were connected, the same or closely related plants and animals inhabited each. After the land masses were separated, the different populations were geographically isolated from each other by great distances of ocean. Life on the different continents had apparently evolved into different species, because the populations were isolated from each other by such great distances.
3.In the 1960s, the past record of geomagnetic reversals was noticed by observing the magnetic stripe "anomalies" on the ocean floor. This results in broadly evident "stripes" from which the past magnetic field polarity can be inferred by looking at the data gathered from simply towing a magnetometer on the sea surface or from an aircraft.

The Cascade Mountain Range, Andes Mountain Range of western South America and the Himalaya Mountain Range are examples of mountain ranges still being formed. The rift valley will widen until it becomes a large basin that fills with sediment from the rift walls and the surrounding area.

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