On the question of what constitutes a lie, the question of intent has more than one aspect. As already discussed, proving that a particular incorrect statement is a deliberate misrepresentation of the truth is challenging – does the person actually know better? Certainly, when a prominent creation science advocate checks out the claim that the dinosaur toes on the Paluxey tracks could have been painted on, finds it to be untrue, but then admits he’s going to continue making the claim to “cover his tail”, he is lying. But true obedience to the command to not bear false witness cannot be restricted to merely not stating known falsehoods. It requires a commitment to truthfulness. Promoting a claim when we have not investigated its truth is also a violation of the commandment. Creation science makes at least an implicit claim to have carefully examined the evidence and found valid justification for its assertions. That is a lie. I have never encountered a young-earth claim that was based on careful research of the evidence. A very popular approach to manufacturing young-earth claims, for example, is to seize on something from a science news article and either claim that it supports a young earth or claim that it is a lie invented by evolutionists, without even looking up the original research behind the article. True honesty applies to other areas as well. Some professional creation science advocates have been dishonest in other areas (e.g., Hovinds on finances, Answers in Genesis in treatment of Creation Ministries International, bogus credentials).
Arguing honestly requires accurately representing the view being addressed, thoroughly examining the relevant evidence, and evaluating it fairly. Asserting that plate tectonics is no good, for example, implies that you have actually examined the evidence, rather than merely heard that it didn’t fit with your preferred idea. In reality, the evidence supporting plate tectonics is extremely extensive, which is why the idea so quickly gained support once it was developed. Kuhn’s “paradigm shift” model ignores the fact that a successful new model needs to explain the data better than the old one. Cranks love to argue “here’s a problem for the existing model, therefore my idea is true”. But that does not prove that your idea is actually an improvement.
Evidence for moving continents accumulated slowly. As soon as decent maps were available, people noticed that South America and Africa could fit up next to each other. But that was merely a curiosity until more extensive geological data were available. By the early 1900’s, geological data showed that features such as mountain chains, faulting patterns, rock types, and fossils also showed patterns consistent with moving continents, but Wegener’s continental drift model was physically unworkable – no viable way of powering it and continents can’t plow through the seafloor. Increasing data about seafloor features, especially after the technological advances forced by World War II, along with paleomagnetic data, proved key for developing an improved model, which proved convincing in the 1960’s.
The magnetic evidence has two main aspects. Just as a compass needle points north, magnetic particles on earth will tend to line up with the Earth’s magnetic field, if they are free to move. But as hot rock cools, or as sediment gets cemented together into rock, the magnetic bits get locked into place. Thus, rocks preserve a record of past magnetic patterns. If the rock moves or the magnetic field changes, it will no longer be aligned. Although the Earth’s field is not as simple as a bar magnet and moves around (being powered by the movement of molten iron in the outer core), to a basic approximation it lines up with the poles. So paleomagnetism can be used to trace which way was north or south as you go into the past. If you examine rocks over time, you find that the magnetic pole indicated by the rocks gets further and further from the current pole over time. When you examine more than one continent, you find that each continent has a different track for the pole. If we allow the continents to move, however, the pole location can be constant and consistent between continents. As the earth is a globe, it has only one north pole, so this supports continental movement over time. Additionally, the magnetic field does not only point north and south; it also has an up or down component. This is obvious if you think about what a compass needle would do if you were at the north magnetic pole – it would point straight down, not towards the actual axis of earth’s rotation. The angle gets steeper as you approach the poles and is about horizontal near the equator. So a measurement of the magnetic angle relative to the horizontal gives a rough measure of how far north or south a rock was when it formed.
The second clue from magnetism comes from the fact that earth’s magnetic field flips from time to time – a compass north needle would point south instead. This can be directly measured by sampling through a series of rock layers. (Various bad young-earth arguments deny or misrepresent the patterns involved.) Thus, the alternating sequence of normal and reversed magnetism is a marker of the passage of time. As new ocean floor rock is produced along the midocean ridges, the rock has the magnetic direction matching the earth’s field. When the field flips, the older rocks out to the side will still have the opposite direction. Going out to either side of the midocean ridge, you find parallel bands of rock alternating between normal and reverse polarity, recording the conveyor belt-like pattern of plates being built at the midocean ridges and then moving out from there.
How can tectonic plates move around on earth’s surface? Evidence that areas of earth’s surface can move up or down was geologically famous by the late 1700’s, but significant sideways motion was more problematic. A major problem with continental drift was that Wegener suggested that continents plow through the seafloor. Seafloor rock is mostly gabbro, which is denser than the granites and gneisses typical of continental crust. If one of those plows through the other, the seafloor would win. But plate tectonics recognized that the seafloor was also moving. Under conditions deep in the mantle, rock behaves differently from familiar conditions on the surface. How do we know? We can measure features such as variations in gravity, heat, and magnetism coming from inside the earth, but the most important measurements come from the patterns in earthquake waves. Two main types of earthquake waves travel through the earth, p waves and s waves. P waves are pressure waves, similar to sound waves, and can travel through fluids. S waves are shear waves and can only travel through solids. Both waves will go faster or slower depending on the density of the rock. By carefully measuring the timing and pattern of earthquake waves around the globe, we can build up a picture of layers inside, a bit like a medical scan. From this, we can detect distinct layers inside the earth, whether global or local regions with distinctive features.
These types of data indicate that there is a significant increase in rock density about 7-10 km below the ocean and about 30-70 km or so below the continents. This is the crust-mantle boundary, or Moho. About another 100 km down, we hit another transition, from lithosphere to asthenosphere. The lithosphere is what makes up tectonic plates. Although rocks can bend some, depending on the pressure, temperature, and amount of time, eventually rock in the lithosphere will usually fail by breaking, generating an earthquake. But the asthenosphere fails by bending and squashing. Thus, lithospheric plates can essentially float on the asthenosphere, moving both vertically and horizontally.
What can power such movement? Wegener did not have an adequate mechanism, but plate tectonics pointed out that the mantle rock could move, with hotter, less dense rock pushing its way up towards the surface, moving sideways, and cooling and sinking down in a slow convection. The plates could ride on that. Ultimately, this is powered by the internal heat of the earth, produced by radioactive decay. Further study showed that there is also the pull from old, cold, dense seafloor rock sinking down into the mantle at the trenches, suction from broken-off chunks of the plate sinking deeper into the mantle (analogous to the suction of trying to pull your foot out of mud), and push out from the midocean ridges as new rock is formed, with the pull from sinking plate edges probably most important.
The midocean ridges are where seafloor is formed. Indeed, we find very young rock there with frequent volcanic activity. Less commonly, we also find places where continents are pulling apart, such as the east African rift valley. Over time, the rock moves sideways, cools, and sinks; islands become undersea guyots; sediment piles up on it. Eventually, it can be shoved down under another plate in a collision at a trench. Continental rock, being less dense, does not squash down deep into the earth very well. Instead, in a collision it pushes up into tall mountain ranges, with long thrust faults where rock has been pushed up and over other rocks. Sometimes plate movement is sideways relative to another plate, producing transform boundaries like the San Andreas fault system.
As plates move, other indicators of location will track with them. A plate may move across a narrow column of hot, rising rock in the mantle. This produces a chain of volcanoes, with older and more eroded volcanoes further and further away in the direction of plate motion. Continents near the poles may have glaciers; areas of plates near the equator will have tropical life forms (such as coal-forming swamps on land or high-nutrient loving plankton in the ocean along the equatorial upwelling zone).
Plate motion produces most earthquakes and volcanoes. Not only the location but also the types are distinctive. Not surprisingly, collisions tend to be more violent than pulling apart. Where a plate edge is being subducted, melting of the sinking rock leads to volcanic arcs above the sinking side. Earthquakes can be very large and can be extremely deep in the earth, as the rigid sinking plate can still have quakes at depths where the surrounding asthenosphere would just squish. As expected, earthquakes show a pattern of getting deeper and deeper as you go from the seafloor trench (where one plate is getting bent and shoved under another) in the direction that the plate is sinking. At diverging boundaries, the earthquakes are not as large, and are all quite shallow – hot rock is rising underneath them, so asthenosphere is not very deep. The faulting is characteristically normal (top side of the fault slid down relative to the bottom side), which is what should be found where two sides are moving apart. At collision zones, the faulting is characteristically reverse, where the top is shoving up and over the bottom. (Unsurprisingly, actual boundaries are complex and can have local movement of various sorts.) Along the transform boundaries, faulting is dominantly strike-slip, with one side grinding past the other. These produce different patterns in the earthquakes, just as the melting of different types of rock with different amounts of mixed-in water leads to different styles of volcanoes at different boundaries.
The movement of plates can be tracked today by GPS. In fact, it affects use of GPS. Over a decade or two, what used to be the exact geographic coordinate of the middle of the road may now be the side of the road, so GPS coordinates must be updated. When we look back at evidence of plate motion through the geologic past, we trace a series of movements, with multiple episodes of plates coalescing into a supercontinent and breaking up again. Both the “expanding earth” claims and some young-earth claims seem to reflect having heard of Pangea and its breakup but nothing more. The whole sequence of plate motions must be accounted for. For example, the rocks here in North Carolina only go back to about 1.2 billion years at the oldest, so much of the total history of the earth is missing. Yet they show evidence of three major episodes of colliding that build supercontinents and the breaking apart of those supercontinents, plus about eight collisions of individual small plates and further movement of those pieces before they became lasting parts of the edge of North America. The impossibility of fitting such long sequences of events into a young-earth timescale is what makes creation science completely untenable, as was recognized in the late 1700’s. The standard young-earth approach of piecemeal excuses to dismiss this or that feature ignores the big picture and completely fails to give any comprehensive model of how the earth works. Just like in politics, it is possible to fool a lot of people by harping on real or imagined faults of the opposition, but actual substance would require demonstrating that your option is consistently better than the alternative.
This is actually a rather brief summary of the geological evidence relating to plate tectonics; many more features are relevant as well. A serious attempt at explaining earth history must take all these data into account, rather than picking out a single feature and claiming to explain it.
