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This region, where the Pacific seafloor is shoving underneath South America, also produced the biggest earthquake ever recorded—and built the Andes mountains. (Scientific American)

Use or video to better understand South America’s earthquakes.

Teachers, scroll down for a quick list of key resources in our Teachers’ Toolkit, including today’s simple MapMaker Interactive map.

Discussion Ideas

• In our video “Earthquakes 101,” we learn that most earthquakes are caused by the movement of tectonic plates far below Earth’s surface. What tectonic plates were interacting in the earthquake that struck Ecuador? Take a look at today’s simple MapMaker Interactive map for some help.
  • The Nazca plate and the South American plate were interacting.

• How were the plates interacting? Take a look at the classic Nat Geo map of “Earth’s Dynamic Crust” for examples of different types of tectonic activity.
  • Subduction! (It’s our favorite geologic process.) According to the “Earth’s Dynamic Crust” map, “Colliding with the edge of a continent [South America], old, cold, heavy seafloor [the Pacific floor of the Nazca plate] drives back into the interior of the Earth and forms an ocean trench. [Look for the Peru-Chile Trench on our map.]. . . The plunging slab also generates heat that melts through the overlying plate, allowing fingers of magma to rise. These fingers form chains of volcanoes like those in the Andes . . . The overriding continent also compresses near the trench, lifting mountains.”
  • Geologists describe the region as having a convergent plate boundary, where two or more tectonic plates bump into each other.
  • Geologists describe the Nazca and South American plate boundaries as forming a thrust fault across the Andes region. A thrust fault, also called a dip-slip fault, is a type of reverse fault, where rock is uplifted during tectonic activity, with a dip of 45 degrees or less.

• The Ecuador quake is described of having a magnitude of about 7.8. What is magnitude? Is 7.8 a high magnitude?
  • Magnitude is a number that describes the intensity or size of an earthquake. Our “Earthquakes 101” video talks about the Richter scale of magnitude, but seismologists are far more likely to use the moment magnitude scale (MMS or simply M).
  • A 7.8 quake has a very high magnitude. The Great San Francisco Earthquake of 1906 had about a 7.8 magnitude, as did the devastating Nepal quake that struck last year. The thrust faults of the Andes were also responsible for the 9.5-magnitude Valdivia earthquake, the largest earthquake ever detected by a quake sensor. The Valdivia earthquake struck southern Chile in 1960.

• The Ecuador quake is described as having a focal depth of about 19.2 kilometers (11.9 miles). What is focal depth? Is 19 kilometers a deep or shallow focal depth?
  • The focal depth of an earthquake is how far below the surface of an earthquake’s epicenter the actual rupture, slip, or dip took place.
  • Earthquakes can take place anywhere between one and 700 kilometers below Earth’s surface, so 19 kilometers is a pretty shallow depth.

• According to the USGS, “Most of the large earthquakes in South America are constrained to shallow depths of 0 to 70 km resulting from both crustal and interplate deformation.” Which geological activity (crustal or interplate deformation) do you think contributed to Ecuador’s quake? See if you can spot the differences between the two types of quakes in the second bookmark of today’s MapMaker Interactive map.
  • The subduction that resulted in Ecuador’s devastating quakes was definitely interplate deformation. “Interplate earthquakes occur due to slip along the dipping interface between the Nazca and the South American plates. Interplate earthquakes in this region are frequent and often large, and occur between the depths of approximately 10 and 60 km.” These quakes often have a higher magnitude, which are represented by darker markers on our map.
    • FYI: “Crustal earthquakes result from deformation and mountain building in the overriding South America plate and generate earthquakes as deep as approximately 50 km.” These quakes often have lower magnitudes, which are represented with lighter blue markers on our map—and often coincide with active volcanoes.

• How is Ecuador’s government responding to the quake? Read through this Washington Post article for some help.
  • President Rafael Correa immediately cut short a visit to Vatican City to lead emergency response efforts.
  • Ecuador has mobilized about 4,600 members of the National Police and 10,400 members of the armed forces to help retain order and assist firefighters and other emergency personnel searching for survivors and victims amid the rubble. Engineers and health professionals have also been dispatched to help affected communities.
  • Business owners and workers are preserving infrastructure to better establish some economic stability. “If we don’t get the stock out, it will go bad, and we’ll lose even more than we already have,” said one man who was retrieving goods from his uncle’s store.
  • Communities are banding together to help each other and organize a network of support. “We will come out of this emergency stronger,” said Vice President Jorge Glas.

• How are other governments responding to the quake? Read through this CNN article for some help.
  • Latin American governments, including Mexico, Peru, Colombia, and Chile, have sent financial aid, supplies, and rescue personnel.
  • The European Union has released €1 million in humanitarian aid and emergency equipment.
  • Other nations, such as Spain, have also sent humanitarian aid.

• How are individuals and NGOs responding to the quake? Read through this Huffington Post article for some help.
  • More than 800 volunteers from the Ecuadorian Red Cross (Cruz Roja) have responded to the disaster with search-and-rescue operations, first aid, and psychosocial support.
  • The Pan-American Health Organization has mobilized emergency response experts to help the government respond with emergency coordination, needs assessment for health services, and clean water and sanitation.
  • UNICEF has established a quake relief fund, as well as delivered 20,000 water-purification tablets.
  • Catholic Relief Services has also established a quake relief fund, and is working with local partners to provide clean water, safe food, and emergency shelters to people made homeless by the quake.
  • Crisis mappers, such as the Standby Task Force, have deployed online teams to compile actionable data to support responding organizations. (Learn more about crisis mapping here.)
  • Ecuadorean community activists have set up a program to raise money for everyday items such as blankets, clothing, canned foods, and mattresses.

TEACHERS’ TOOLKIT

Scientific American: Ecuador Quake is on Fault That Generates Monster Shakers

Nat Geo: Earthquakes 101

USGS: M7.8 – 27km SSE of Muisne, Ecuador

Nat Geo: April 2016 Ecuador Quake MapMaker Interactive map

Standby Task Force: Ecuador Earthquake