Queen Charlotte Fault facts for kids

Tectonic map of Alaska and northwestern Canada showing main faults and historic earthquakes

The Queen Charlotte Fault is a very active crack in the Earth's crust. It marks the boundary where two huge pieces of the Earth's surface, called tectonic plates, slide past each other. These plates are the North American plate and the Pacific plate. Think of it like two giant puzzle pieces grinding alongside each other!

This fault is located off the coast of Canada and Alaska. It's similar to the famous San Andreas Fault in California, which also involves plates sliding sideways. The Queen Charlotte Fault is one of the fastest-moving fault systems in the world. The plates here slide past each other at about 50 millimeters (about 2 inches) every year. This constant movement causes many earthquakes.

The fault is named after the Queen Charlotte Islands (now called Haida Gwaii), which are near its southern end. As it stretches northward along the Alaskan coast, it's known as the Fairweather Fault. Together, these two parts form the Queen Charlotte-Fairweather Fault System. Over the last 100 years, this system has caused at least seven major earthquakes, each stronger than magnitude 7.

How Plates Move Along the Fault

The Queen Charlotte Fault isn't just a simple straight line where plates slide perfectly past each other. Sometimes, the plates also push into each other a little bit. This combination of sliding and pushing is called "transpression."

The way the plates move and interact changes along the fault's long path. Scientists have divided the fault into three main sections:

• Southern Section: Here, the plates push into each other more strongly. This can cause the Earth's crust to buckle and lift, leading to a type of earthquake called a thrust earthquake.
• Central Section: In this part, there's still some pushing, but it's less intense than in the south. The seafloor here looks different, with various ridges and basins forming.
• Northern Section: This section is mostly about the plates sliding sideways past each other. It's a more direct "strike-slip" motion, like the San Andreas Fault.

These different movements mean that the types of earthquakes and how the land changes can vary greatly from one part of the fault to another. For example, a change in the Pacific plate's movement millions of years ago increased the pushing motion, especially in the southern section. This led to the 2012 Haida Gwaii earthquake, which was a thrust earthquake.

Southern Section: Pushing and Buckling

In the southern part of the Queen Charlotte Fault, the plates don't just slide; they also press against each other. This causes the Earth's crust to deform, meaning it changes shape. For instance, the 2012 Haida Gwaii earthquake was a "thrust" earthquake. This means one plate was pushed up and over the other, rather than just sliding sideways.

Scientists have observed that the seafloor west of Haida Gwaii has buckled downwards, and new cracks (called normal faults) have formed. There's also a feature called the Queen Charlotte Terrace, which is like a pile of squished rock layers that have built up over time due to the plates pushing together. Studies using GPS and other tools confirm that there's a shallow "thrust" boundary here, where one plate is trying to slide underneath the other.

Central Section: A Mix of Movements

As you move north to the central section of the fault, the way the seafloor looks and the structures beneath it change. The Queen Charlotte Terrace becomes wider and deeper, forming a series of slanted ridges and basins.

Here, the pushing motion between the plates is less strong than in the south. This change in how the plates interact leads to a different kind of stress on the rocks. It's a transition from mostly squeezing in the south to more of a sideways tearing motion in the central part.

Northern Section: Mostly Sliding Sideways

The northern section of the Queen Charlotte Fault is where the plates mostly slide past each other in a direct sideways motion. This is called a "strike-slip" movement. The 2013 Craig, Alaska earthquake was a good example of this type of earthquake.

In this area, the seafloor shows a simpler pattern, with most of the movement happening along one main crack. This part of the fault has been the source of many powerful earthquakes. It's also where other smaller faults and fracture zones meet the Queen Charlotte Fault, adding to the complex geology of the region.

Major Earthquakes Along the Fault

The Queen Charlotte-Fairweather Fault System has caused some of the biggest earthquakes in Canada and Alaska. Here are some of the most significant ones:

• 1949 Queen Charlotte Islands Earthquake: This was a massive magnitude 8.1 earthquake, the largest ever recorded in Canada. It caused a nearly 500-kilometer (310-mile) section of the fault to break. The ground moved mostly sideways during this event. It caused landslides and damage to buildings and roads.

• 1958 Lituya Bay Earthquake: This magnitude 7.8 earthquake in Alaska caused a huge landslide into Lituya Bay. This landslide created a "megatsunami" – an incredibly tall wave that reached a height of 524 meters (1,720 feet) as it crashed into a mountainside. This is the tallest tsunami ever recorded!

• 2012 Haida Gwaii Earthquake: A powerful magnitude 7.8 earthquake struck off the coast of Haida Gwaii on October 27, 2012. It was the biggest earthquake in Canadian territory since 1949. While it caused a small tsunami (about 45 centimeters or 1.5 feet locally), its main impact was the temporary drying up of hot springs on Hotspring Island. This earthquake was unusual because it was a "thrust" earthquake, meaning the plates pushed over each other, rather than just sliding sideways. This type of movement is more common in areas like the Cascadia subduction zone to the south.

See Also

• List of earthquakes in Canada
• Queen Charlotte Sound
• Ring of Fire