Impacts of Earthquake on Tree Growth and 8 Other Changes

Impacts of Earthquake on Tree Growth

Earthquakes are not only synonymous with destruction, but they can also create forests – at least for a short time. Strong earthquakes can help trees grow by flooding the soil around their roots with additional water. 

These fleeting bursts of growth leave traces in wood cells that can also be used to detect and date ancient earthquakes more accurately.

Before jumping to the study and its result, let’s first know the impacts of earthquakes. What kind of geographical changes does the Earth go through during and after the tremors?

Causes of Earthquake 

What causes Earthquake | Copyright: The Telegraph

Earthquakes are tremors manifest in the Earth’s crust, the outermost layers of the world. 

From a technical point of view, earthquakes are a release of energy accumulated below the ground, a release that causes the rock blocks to settle, giving rise to tremors.

Earthquakes are measured on the Richter Scale index in terms of intensity. It ranges from 1 for the weakest to 10 for the strongest. 

However, there have never been any records of an earthquake that managed to reach the maximum rate. The strongest earthquake ever cataloged occurred in Chile in May 1960 and reached 9.5 on the Richter Scale.

There are three leading causes for tremors in the Earth’s crust: collapse, volcanism, and tectonism.

1. Collapse

The tremors caused by the collapse are of minor importance. They are caused by some internal accommodation, caused by the rupture or slippage of inner rock blocks, usually sedimentary, which are generally less resistant types of rock. The intensity of these jolts is low.

2. Volcanism

The tremors caused by volcanism may be more robust in areas close to volcanoes. 

They occur from some internal rupture or eruption of magma or trapped gases under high pressure. Its effects are not usually felt over long distances.

3. Tectonism

Tectonism, in turn, can be considered the main “villain” responsible for earthquakes. As we know, the Earth’s crust is not a single layer but made up of numerous blocks, called tectonic plates. 

Many of these plates are constantly colliding, taking opposite directions. In this contact zone, most of the world’s earthquakes occur.

Furthermore, when the force of contact between these plates is stronger than the resistance of the rocks, they break up. 

They form the so-called geological Faults, common in the contact zones between two plates, and manifest themselves less frequently in more stable areas. 

When these Faults cause the rock blocks to resettle, earthquakes occur. The biggest Fault in the world is found in the United States: the San Andreas fault.

How Earthquake Affects Tree Growth?

graph showing a tree growth acceleration after an earthquake - the impact of an earthquake
The light green section of the figure highlights modeled tree growth in Chilean Coast, showing the growth accelerating after the earthquake (represented by orange dotted line) | Research by Christian H. Mohr

New research conducted by the University of Potsdam in Germany reveals how earthquakes can contribute to tree growth by changing groundwater availability.

Research has found that considerable tree growth is detected when aftershocks subside, and researchers have now found evidence of this link. 

Hydrologist Christian Mohr of the University of Potsdam and lead author of the study explained that large earthquakes could increase the amount of water supply flows, raising groundwater levels. In this way, plant roots have more water resources under normal conditions. 

“If tree growth is limited primarily by water, trees should, in theory, record hydrological responses to earthquakes, altering their growth rates,” added Mohr.

If the change in hydrological flow contributes to tree growth, then this relationship is registered in the trunks.

To evaluate this hypothesis, Mohr and his team analyzed Pinus radiata pine trees, located in Chile, in the Maule region, which, in 2010, was severely affected by an earthquake measuring 8.8. 

From the analysis of tree trunk rings collected in 2014, the researchers found that some trees in the valley experienced a temporary increase in growth right after the tremors.

In addition to the tree trunk ring growth, the researchers also analyzed the proportion of carbon isotopes in these species cells. 

Such evidence provided a broad perspective on trees’ health, growth, and water availability. 

In contrast, some trees located on the slopes behaved similarly, indicating that the effect of the earthquake was mild and temporary — lasting a matter of weeks.

The discovery reveals how this technique can be applied in studies of ancient earthquakes. 

Researchers say it shows that post-seismic changes recorded in the trunk rings and the number of carbon isotopes can respond to tree growth and photosynthetic responses to tremors. 

“They can offer a tree-based approach to paleoseismology,” the team added. The research was published in the journal JGR Biogeosciences.

Other Impacts of Earthquake

On average, about a million earthquakes occur per year on the planet. The vast majority are so small that they go unnoticed. 

However, based on observations since 1990, there are 17 earthquakes each year with a magnitude greater than seven on the Richter scale.

A large one above 8, according to the United States Geological Survey. A strong earthquake can bring many changes on our planet you may not know about, such as:

1. An earthquake can change the length of the day

In March 2011, an 8.9-magnitude earthquake struck northeast Japan. The energy it released was such that it altered the distribution of the Earth’s mass, and this generated a slight acceleration in its rotational speed.

As a result, the day on the planet lasted 1.8 microseconds less than usual.

NASA scientists studying the Indonesian earthquake of December 26, 2004, have calculated that it slightly changed the shape of our planet, shortened the length of the day by almost 3 microseconds, and shifted the North Pole by several centimeters.

2. Stagnant water smells funny before an earthquake 

radon emission from underground at Osaka earthquake 2018 - impacts of an earthquake
Exhalation of Radon (222Rn) gas from underground at Osaka RI facility | Illustration by Jun Muto

Ponds, canals, lakes, and other sources of standing water can give off an unpleasant odor and slightly increase in temperature before an earthquake.

It is due to underground gases that are released as tectonic plates move. Gases can also contribute to changing the behavior of wildlife in the area.

3. Animals change their behavior due to seismic activity 

Researchers from the Department of Sciences of the Open University in the United Kingdom observed, for example, the disappearance of toads before the 2009 earthquake in Italy. 

Toads are also believed to detect changes in the chemical composition of water caused by stress on rocks.

But it’s not just toads; before the 2004 Indonesia earthquake and tsunami, witnesses reported seeing some animals and birds making their way to high ground. 

Scientists believe that animals can sense the slight tremors that occur before an earthquake or possibly detect the electrical signals caused by the movement of underground rocks. 

4. Surface Break

An earthquake tremor is caused by the rupture of a fault in the depths of the Earth. This rupture can sometimes reach the Earth’s surface, referred to as a surface break. 

This relative displacement of the ground on either side of the Fault is permanent. 

The accumulation over time of similar earthquakes contributes to creating the reliefs that characterize the regions close to the faults. This permanent displacement on the Fault is frequent for high magnitude earthquakes. 

There is indeed a relationship between the magnitude of the earthquake and the size of the broken Fault. The surface emergence of the Fault is frequently observed when the magnitude exceeds 6. 

Landscape modifications can be particularly significant during large earthquakes with vertical displacement (for example, in central Italy in 2016).

5. After an earthquake, the seiches come 

Seiche illustrated as standing waves - impacts of an earthquake
Visualization of Standing waves in a Seiche | Illustrated by NOAA

After an earthquake, internal standing waves are often formed in the water, known as seiche in pools and lagoons. 

The key to developing a seiche that can be invisible to the naked eye is that the body of water is at least partially delimited, as is the case of a swimming pool.

6. Cause Tsunami

If an earthquake significantly changes the topography of the seabed, it can largely displace a large volume of water suddenly. 

This wave, propagating first over a deep-sea domain, has a low amplitude, a long wavelength, and a high speed. 

As you approach land, the depth decreases, the amplitude of this wave increases: the tsunami then floods the coastal plain.

The most significant known tsunamis of seismic origin have generated floods over several kilometers inland and waves reaching several tens of meters, such as the case in tsunamis of Valdivia and Maule in Chile in 1960 and 2010, respectively, tsunamis of Indonesia in 2004 and Japan in 2011. 

The latter caused the nuclear accident at the Fukushima Daiichi nuclear power plant.

7. Gravity Movements

Seismic tremors can destabilize rock masses whose balance is precarious. This phenomenon occurs mainly along the slopes in mountainous areas. 

These movements can take different forms: landslides, falling blocks, mudslides.

8. Phenomenon Of Liquefaction

illustration of soil comparison after and before the earthquake - impacts of an earthquake
The soil condition before (above) and after the (below) earthquake | Figure by Yukitaje Shioi

The liquefaction phenomenon occurs in loosely cohesive soils (typically sands) saturated with water. 

The pressure variations during the passage of seismic shocks set the water in motion and cause contact between the grains of the sand layer to be lost, which reduces or even cancels its shear resistance. 

This layer then behaves like a liquid, and the soil can no longer support the weight of the layers. These, which have remained rigid, can fracture and allow the “liquid” to escape on the surface. 

During earthquakes, we often observe sand “volcanoes” of varying sizes. In extreme cases, constructions can be destabilized and sometimes sink into the ground.

Conclusion

The earthquakes themselves are not as destructive as is generally believed. Instead, the subsequent processes of earthquakes bring great suffering to people in earthquake-prone areas.

However, the recent study highlighted the positive impact of earthquakes on the planet’s climate and biodiversity. 

More research and investigation are still needed for an earthquake and other disasters, but the word synonymous with destruction is not that bad after all.