Archive for the ‘Geophysics’ Category

The Age(s) of the Continents

Wednesday, August 6th, 2008

by Dr. Jeffrey Zweerink

Photo of Jeff ZweerinkThe Hebrew phrase “tōhū wābōhū” provides the first description of Earth given in Genesis 1. Many English Bible translations render this description as “formless and void (or empty)”. The Hebrew words imply that Earth’s surface was a desolate, undistinguishable ruin. Genesis 1:3 through Genesis 2:3 delineates how God transformed this wasteland into a variety of habitats teeming with life.

One critical transformation involves breaking up the formless deep to form land upon which humans will live. On the third day of the creation week, Moses, the likely author of Genesis, declares that waters below the heavens were “gathered into one place” in order to “let the dry land appear”. In RTB’s creation model, this declaration means that scientists should find that the formation of a large, permanent continental landmass occurred within a definite time window (or burst) in Earth’s history. Additionally, that time window must close before the Cambrian explosion (which occurred around 540 million years ago), when complex multicellular life appeared on Earth.

Past research on zircons revealed that most continental land dated to either 1.2, 1.9, 2.7, or 3.3 billion years ago. The clustering around these dates indicates that continental growth did occur in bursts. However, such clustering would also result from preferential preservation of crust that grew uniformly.

More recent research adds further support to the idea that continental growth occurred in bursts. For continents to grow, regions of the mantle must melt and differentiate in order to provide the additional continental material. One particularly useful way to measure the melting of mantle material is the Rhenium-Osmium radioactive decay channel. A team of scientists using this decay channel discovered that mantle melting events also clustered around 1.2, 1.9, and 2.7 billion years ago. (No materials dating older than 3 billion years were used in the study.)

The clustering of the continental ages and the mantle melting events around the same ages is extremely unlikely. Therefore, taken together, these results argue that the bulk of continent formation occurred in a time window between 3.3 and 1.2 billion years ago. Thus, these discoveries demonstrate a way the Creator could have “let the dry land appear” and add to the body of evidence supporting RTB’s creation model.

Getting the Continental Drift

Wednesday, July 9th, 2008

by Jeff Zweerink

Photo of Jeff ZweerinkEarthquakes and volcanos serve as important reminders of the phenomenal forces at work underneath Earth’s surface. The shape and arrangements of the continents change as the massive tectonic plates float across the more fluid upper mantle. This tectonic activity changed the initial, water-covered state of Earth, covering roughly 30% of the planet with continents. Additionally, it replaces continental landmass lost to erosion.

Every few hundred million years all the continents group together to form supercontinents such as Pangaea and Rodinia. Eventually, these supercontinents split up and start a new cycle of continental drift that eventually forms a new supercontinent.

While an abundance of geological data records the motions of the continents over time, scientists have struggled to model such behavior in the lab. However, two New York University scientists have recently built a model that demonstrates cyclic behavior analogous to the recorded continental drift. Their model includes a high-viscosity glycerin/water mixture with heavier-than-water plastic beads (which play the role of continents). The model is heated and cooled in a way reflective of processes operating inside Earth.

When the model was heated and cooled in the absence of the beads, the glycerin/water mixture flowed in a circle for long periods of time without change. Upon adding the beads, the circulation pattern reversed directions every few hours. Thus, they conclude that the continents play a critical role in the cyclic building of supercontinents. The thermal mass associated with the continents affects the flow of rock in the underlying mantle, causing it to change directions periodically. Previous thinking assumed that continents simply rode along on the flow of mantle rock.

Without the flow reversal, the supercontinent would never split apart to begin a new cycle and plate tectonics would eventually grind to a halt. While this change would eliminate earthquakes, the loss of tectonic activity would also rapidly (on geological timescales) lead to an uninhabitable Earth. This research provides scientists with another tool for exploring how well-designed Earth’s interior processes support life.

Design Feature Prevents Hard Snowball Earth

Wednesday, March 12th, 2008

by Jeff Zweerink

Photo of Jeff ZweerinkImagine the Antarctic glaciers extending over the whole Earth. Dating back to the early 1960s, scientists proposed just such a scenario, known as a “snowball Earth” hypotheses to explain various geological and geochemical data in the planet’s history.

According to the proposal, a snowball Earth could possibly form when the planet experiences periods of increased glaciation (or ice ages) due to variations in its orbit around the Sun. As Earth’s temperature drops, glaciers around the north and south poles begin to grow and spread toward the equator. Snow and ice reflect more sunlight than rock, vegetation, and water, causing a further decrease in the global climate. If the glaciers reach close enough to the equator, the increased cooling might result in the complete covering of Earth with glaciers.

During the Cryogenian geological period (850-630 million years ago), two extensive glaciations occurred which may have resulted in snowball Earth. Presumably, continued volcanic action produced enough greenhouse gas emissions to reverse these hypothesized snowball Earth conditions. A thick glacial covering would dramatically impact life on Earth. In fact, these two extensive glaciations immediately preceded the Cambrian Explosion. However, if an abundance of organic carbon sediments covers the ocean floors, then a mechanism exists to prevent snowball scenarios.

An article published in Nature describes the discovery of one preventive mechanism. As the global temperature decreases with the advance of the glaciers, the oceans dissolve more oxygen from the atmosphere. Consequently, this oxygen reacts with the buried organic carbon to produce carbon dioxide, which then enters the atmosphere. The resulting increase in greenhouse heating prevents the further advance of the glaciers.

Because abundant life has existed for about 3.5 to 3.8 billion years of Earth’s history, an ample supply of deep ocean organic carbon has always existed to prevent a snowball Earth. While the snowball Earth hypotheses remain debatable, they do highlight a few apologetic points.

  1. A snowball Earth provides one more mechanism that can severely disrupt a planet’s capacity to support life.

  2. Scientists continue to find evidence that Earth’s habitability relies on an intricate interplay of geological (glaciation), astronomical (variations in Earth’s orbit), and biological (abundant deep-ocean organic carbon remains) processes.

Both of these points attest to the difficulty, from a naturalistic perspective, of attaining conditions suitable for life. That Earth has remained habitable throughout most of its history comports well with the idea that a super-intelligent Designer fashioned Earth intending to fill it with life.