Flood Basalts & Trap Events – What Are They?

This post will be the first in a series of articles discussing flood basalts, trap events, and the largest volcanic events that have occurred in earth’s history.

What are Flood Basalt Eruptions?

Flood basalt eruptions are eruptions that erupt an enormous volume of basaltic magma over an extended period of time. By volume, flood basalts are the largest volcanic events that occur on our planet, with some basalt provinces erupting enough magma to cover the entirety of the United States in magma more than 1 kilometer deep (if spread evenly). Flood basalt eruptions are often referred to as “trap” events, as the eruptions often result in the formation of trap formations (a geological term for a specific type of rock formation).

trap formation
Example picture of an ancient volcanic trap formation.

While the volumes of flood basalts are beyond imaginable scale, it is important to note that the time-span of these events can often stretch for longer than one million years. As such, flood basalts aren’t really singular-eruption events. They are more accurately defined as a large-scale magmatic event that occurs over a long period of time. Thankfully, flood basalt eruptions are extremely rare, and may be separated by time periods as long as multiple millions of years.  The most recent event was the Columbia River basalt group, which started approximately 17 million years ago.

What Causes Flood Basalt Eruptions?

The causes of flood basalt eruptions are not entirely understood. There is a lot of ongoing research and study on the causes and effects of flood basalt events. Also, there is a strong possibility that flood basalt provinces can form as a result of different geological processes.

As an example of this, there are many flood basalt provinces that are associated with continental break-up and extreme rifting events. When Africa and South America split, there were some massive flood basalts such as the Parana-Etendaka traps, which may have also resulted in some of the largest explosive eruptions that have ever occurred.

On the other hand, many flood basalt provinces are not associated with the break-up or splitting of continents. The well-known Columbia River Basalt group, which is possibly associated with the Yellowstone hotspot, was not associated with any well-known rifting or continental breakup. Many other large-volume flood basalt type events have occurred in the ocean, which are not associated with known rifting-events.

Map of some of the more recently flood basalt formations. Many older and very large flood basalts have been discovered around the world, but are not well-studied or researched due to their age and how much erosion there has been.

Flood Basalts and Hotspots

For most flood basalt events, the simple reality is that there needs to be an absurd and continuous supply of magma for these events to occur. As a result, it is more or less established that volcanic hotspots are the cause behind every flood basalt event. With that said, hotspots alone are not well understood. Many volcanic hotspots behave very different from other hotspots, and what causes them to form may vary greatly.

One theory that may be slightly further out there, but still a possibility is that flood basalt events are associated with asteroid or meteor impact events. This theory is known as antipodal impact theory, although there are a many flaws and inconsistencies that make this theory nothing more than a simple theory.

Flood Basalts and Extinction Events

One of the most worrisome aspects of flood basalt eruptions is the fact that they are strongly correlated with many of the world’s largest extinction events. The P/T extinction event, where over 95% of marine life ceased to exist, and over 70% of land-based life perished is thought to be related to the Siberian Traps flood basalt event.

While a new flood basalt-style eruption would be extremely damaging to the world if it were to occur in the near geological future, one thing we could be thankful for is the fact that it would take a very long time  (likely more than 100,000 years) before it would actually start to  cause extinctions. The reason for this is that flood basalt events cause extinctions as the result of mass climate change by overloading the planet’s atmosphere and ecosystem with gases such as Co2, Sulphur Dioxide, and other damaging components.

The resulting overload of gases in the environment caused mass climate-change, which then resulted in a long series of chain reactions leading to oceanic anoxia and complete ecosystem collapse.

Is Iceland a Flood Basalt Province?

Many people consider Iceland an active flood basalt province, although the eruption / effusion rate is not high enough to actually cause any harm to the earth. For flood basalt events to actually damage the environment to a large degree, they would have to produce volcanic gases at a higher rate than the environment could cleanse and remove those gases from the atmosphere. In Iceland’s case, the eruption rate is not high enough, and most of the volcanic gases are being removed from the atmosphere quicker than they are accumulating.

Modern Climate Change and Global Warming Mimics Flood Basalt Events

While it is extremely unlikely that we will see a new flood basalt event begin in our lifetime, one major concern is the fact that current global warming via the injection of carbon dioxide into the atmosphere is doing the exact same thing that flood basalt events did, except on a much quicker time-scale.

To many scientists, the study of flood basalt events and resulting extinctions via climate change  has been a wake-up call when looking at the current issues of global warming.

Conclusions

Flood basalt events are the largest known volcanic events that occur on the Earth. They are extremely rare, but produce absurd volumes of effusive magma that can lead to extinction events and mass disruption to the Earth’s climate.